diff --git a/app/models/import_job.rb b/app/models/import_job.rb
index c0b6a2d2e..9192b98bd 100644
--- a/app/models/import_job.rb
+++ b/app/models/import_job.rb
@@ -34,6 +34,25 @@ class ImportJob < ApplicationModel
     save
   end
 
+  # Gets called when the Scheduler gets (re-)started and this job was still
+  # in the queue. If `finished_at` is blank the call is piped through to
+  # the ImportJob backend which has to decide how to go from here. The delayed
+  # job will get destroyed if rescheduled? is not implemented
+  # as an ImportJob backend class method.
+  #
+  # @see Scheduler#cleanup_delayed
+  #
+  # @example
+  #  import.reschedule?(delayed_job)
+  #
+  # return [Boolean] whether the ImportJob should get rescheduled (true) or destroyed (false)
+  def reschedule?(delayed_job)
+    return false if finished_at.present?
+    instance = name.constantize.new(self)
+    return false if !instance.respond_to?(:reschedule?)
+    instance.reschedule?(delayed_job)
+  end
+
   # Convenience wrapper around the start method for starting (delayed) dry runs.
   # Logs the start and end time (if ended successfully) and logs
   # exceptions into result if they happen.
diff --git a/app/models/scheduler.rb b/app/models/scheduler.rb
index 47ff10290..0b2825abe 100644
--- a/app/models/scheduler.rb
+++ b/app/models/scheduler.rb
@@ -11,6 +11,9 @@ class Scheduler < ApplicationModel
 
     Thread.abort_on_exception = true
 
+    # cleanup old background jobs
+    cleanup
+
     # start worker for background jobs
     worker
 
@@ -44,6 +47,80 @@ class Scheduler < ApplicationModel
     end
   end
 
+  # Checks all delayed jobs that are locked and cleans them up.
+  # Should only get called when the Scheduler gets started.
+  #
+  # @see Scheduler#cleanup_delayed
+  #
+  # @param [Boolean] force forces the cleanup if not called in Scheduler starting context.
+  #
+  # @example
+  #   Scheduler.cleanup
+  #
+  # @raise [RuntimeError] If called without force and not when Scheduler gets started.
+  #
+  # return [nil]
+  def self.cleanup(force: false)
+
+    if !force && caller_locations.first.label != 'threads'
+      raise 'This method should only get called when Scheduler.threads are initialized. Use `force: true` to start anyway.'
+    end
+
+    Delayed::Job.all.each do |job|
+      cleanup_delayed(job)
+    end
+  end
+
+  # Checks if the given job can be rescheduled or destroys it. Logs the action as warn.
+  # Works only for locked jobs. Jobs that are not locked are ignored and
+  # should get destroyed directly.
+  # Checks the delayed job object for a method called .reschedule?. The memthod is called
+  # with the delayed job as a parameter. The result value is expected as a Boolean. If the
+  # result is true the lock gets removed and the delayed job gets rescheduled. If the return
+  # value is false it will get destroyed which is the default behaviour.
+  #
+  # @param [Delayed::Job] job the job that should get checked for destroying/rescheduling.
+  #
+  # @example
+  #   Scheduler.cleanup_delayed(job)
+  #
+  # return [nil]
+  def self.cleanup_delayed(job)
+    return if job.locked_at.blank?
+
+    job_name       = job.name
+    payload_object = job.payload_object
+    reschedule     = false
+    if payload_object.present?
+      if payload_object.respond_to?(:object)
+        object = payload_object.object
+
+        if object.respond_to?(:id)
+          job_name += " (id: #{object.id})"
+        end
+
+        if object.respond_to?(:reschedule?) && object.reschedule?(job)
+          reschedule = true
+        end
+      end
+
+      if payload_object.respond_to?(:args)
+        job_name += " - ARGS: #{payload_object.args.inspect}"
+      end
+    end
+
+    if reschedule
+      action = 'Rescheduling'
+      job.unlock
+      job.save
+    else
+      action = 'Destroyed'
+      job.destroy
+    end
+
+    Rails.logger.warn "#{action} locked delayed job: #{job_name}"
+  end
+
   def self.start_job(job)
 
     Thread.new {
diff --git a/lib/import/base.rb b/lib/import/base.rb
index 3bfe7f41f..331772f1c 100644
--- a/lib/import/base.rb
+++ b/lib/import/base.rb
@@ -3,7 +3,7 @@
 module Import
   class Base
 
-    # Checks if the able to get queued by the scheduler.
+    # Checks if the backend is able to get queued by the Scheduler.
     #
     # @example
     #  Import::ExampleBackend.queueable?
@@ -14,7 +14,20 @@ module Import
       true
     end
 
-    # Initializes a new instance with a stored reference to the import job.
+    # Checks if the backend is able to get rescheduled in case the Scheduler
+    # got (re-)started while this ImportJob was running. Defaults to false.
+    #
+    # @example
+    #  instance = Import::LDAP.new(import_job)
+    #  instance.reschedule?(delayed_job)
+    #  #=> false
+    #
+    # return [false]
+    def reschedule?(_delayed_job)
+      false
+    end
+
+    # Initializes a new instance with a stored reference to the ImportJob.
     #
     # @example
     #  instance = Import::ExampleBackend.new(import_job)
diff --git a/lib/import/ldap.rb b/lib/import/ldap.rb
index e817762e3..5b82e60a4 100644
--- a/lib/import/ldap.rb
+++ b/lib/import/ldap.rb
@@ -32,6 +32,24 @@ module Import
       start_import
     end
 
+    # Gets called when the Scheduler gets (re-)started and a LDAP ImportJob was still
+    # in the queue. The job will always get restarted to avoid the gap till the next
+    # run triggered by the Scheduler. The result will get updated to inform the user
+    # in the agent interface result view.
+    #
+    # @example
+    #  instance = Import::LDAP.new(import_job)
+    #  instance.reschedule?(delayed_job)
+    #  #=> true
+    #
+    # return [true]
+    def reschedule?(_delayed_job)
+      @import_job.update_attribute(:result, {
+                                     info: 'Restarting due to scheduler restart.'
+                                   })
+      true
+    end
+
     private
 
     def start_import
diff --git a/spec/lib/import/base_spec.rb b/spec/lib/import/base_spec.rb
index d1323ed7a..148c6c5f6 100644
--- a/spec/lib/import/base_spec.rb
+++ b/spec/lib/import/base_spec.rb
@@ -23,4 +23,15 @@ RSpec.describe Import::Base do
       end.to raise_error(RuntimeError)
     end
   end
+
+  describe '#reschedule?' do
+
+    it 'returns false by default' do
+      import_job  = create(:import_job)
+      instance    = described_class.new(import_job)
+      delayed_job = double()
+
+      expect(instance.reschedule?(delayed_job)).to be false
+    end
+  end
 end
diff --git a/spec/lib/import/import_job_backend_examples.rb b/spec/lib/import/import_job_backend_examples.rb
index a72c3e74e..acca289e5 100644
--- a/spec/lib/import/import_job_backend_examples.rb
+++ b/spec/lib/import/import_job_backend_examples.rb
@@ -1,6 +1,6 @@
 RSpec.shared_examples 'ImportJob backend' do
 
-  it 'responds to #queueable?' do
+  it 'responds to .queueable?' do
     expect(described_class).to respond_to(:queueable?)
   end
 
@@ -16,8 +16,13 @@ RSpec.shared_examples 'ImportJob backend' do
     end.not_to raise_error
   end
 
-  it 'responds to .start' do
+  it 'responds to #start' do
     import_job = create(:import_job)
     expect(described_class.new(import_job)).to respond_to(:start)
   end
+
+  it 'responds to #reschedule?' do
+    import_job = create(:import_job)
+    expect(described_class.new(import_job)).to respond_to(:reschedule?)
+  end
 end
diff --git a/spec/lib/import/ldap_spec.rb b/spec/lib/import/ldap_spec.rb
index 645c45a2c..1359c8904 100644
--- a/spec/lib/import/ldap_spec.rb
+++ b/spec/lib/import/ldap_spec.rb
@@ -4,7 +4,7 @@ require 'lib/import/import_job_backend_examples'
 RSpec.describe Import::Ldap do
   it_behaves_like 'ImportJob backend'
 
-  describe '::queueable?' do
+  describe '.queueable?' do
 
     it 'is queueable if LDAP integration is activated and configured' do
       allow(Setting).to receive(:get).with('ldap_integration').and_return(true)
@@ -86,4 +86,30 @@ RSpec.describe Import::Ldap do
       end
     end
   end
+
+  describe '#reschedule?' do
+
+    it 'initiates always a rescheduling' do
+      import_job  = create(:import_job)
+      instance    = described_class.new(import_job)
+      delayed_job = double()
+
+      expect(instance.reschedule?(delayed_job)).to be true
+    end
+
+    it 'updates the result with an info text' do
+      import_job  = create(:import_job)
+      instance    = described_class.new(import_job)
+      delayed_job = double()
+
+      expect do
+        instance.reschedule?(delayed_job)
+      end.to change {
+        import_job.result
+      }
+
+      expect(import_job.result.key?(:info)).to be true
+    end
+
+  end
 end
diff --git a/spec/models/import_job_spec.rb b/spec/models/import_job_spec.rb
index 638277451..adb6d1a88 100644
--- a/spec/models/import_job_spec.rb
+++ b/spec/models/import_job_spec.rb
@@ -10,10 +10,28 @@ RSpec.describe ImportJob do
         end
       end
     end
+
+    module Import
+      class NoRescheduleMethod
+
+        def initialize(import_job)
+          @import_job = import_job
+        end
+
+        def start
+          @import_job.result = { state: 'Done' }
+        end
+
+        def reschedule?(_delayed_job)
+          'invalid_but_checkable_result'
+        end
+      end
+    end
   end
 
   after do
     Import.send(:remove_const, :Test)
+    Import.send(:remove_const, :NoRescheduleMethod)
   end
 
   let(:test_backend_name) { 'Import::Test' }
@@ -197,4 +215,29 @@ RSpec.describe ImportJob do
     end
   end
 
+  describe '.reschedule?' do
+
+    it 'returns false for already finished jobs' do
+      instance    = create(:import_job)
+      delayed_job = double()
+
+      instance.update_attribute(:finished_at, Time.zone.now)
+
+      expect(instance.reschedule?(delayed_job)).to be false
+    end
+
+    it 'returns false for backends not responding to reschedule?' do
+      instance    = create(:import_job)
+      delayed_job = double()
+
+      expect(instance.reschedule?(delayed_job)).to be false
+    end
+
+    it 'returns the backend reschedule? value' do
+      instance    = create(:import_job, name: 'Import::NoRescheduleMethod')
+      delayed_job = double()
+
+      expect(instance.reschedule?(delayed_job)).to eq 'invalid_but_checkable_result'
+    end
+  end
 end
diff --git a/spec/models/scheduler_spec.rb b/spec/models/scheduler_spec.rb
new file mode 100644
index 000000000..6f9302e65
--- /dev/null
+++ b/spec/models/scheduler_spec.rb
@@ -0,0 +1,128 @@
+require 'rails_helper'
+
+RSpec::Matchers.define_negated_matcher :not_change, :change
+
+RSpec.describe Scheduler do
+
+  before do
+    module SpecSpace
+      class DelayedJobBackend
+
+        def self.start
+          # noop
+        end
+
+        # rubocop:disable Style/TrivialAccessors
+        def self.reschedule=(reschedule)
+          @reschedule = reschedule
+        end
+
+        def self.reschedule?(_delayed_job)
+          @reschedule || false
+        end
+      end
+    end
+  end
+
+  after do
+    SpecSpace.send(:remove_const, :DelayedJobBackend)
+  end
+
+  describe '.cleanup' do
+
+    it 'gets called by .threads' do
+      expect(described_class).to receive(:cleanup).and_throw(:called)
+      expect do
+        described_class.threads
+      end.to throw_symbol(:called)
+    end
+
+    context 'not called from .threads method' do
+
+      it 'throws an exception' do
+        expect do
+          described_class.cleanup
+        end.to raise_error(RuntimeError)
+      end
+
+      it 'throws no exception with force parameter' do
+        expect do
+          described_class.cleanup(force: true)
+        end.not_to raise_error
+      end
+    end
+
+    # helpers to avoid the throwing behaviour "describe"d above
+    def simulate_threads_call
+      threads
+    end
+
+    def threads
+      described_class.cleanup
+    end
+
+    it 'keeps unlocked Delayed::Job-s' do
+      # meta :)
+      described_class.delay.cleanup
+
+      expect do
+        simulate_threads_call
+      end.not_to change {
+        Delayed::Job.count
+      }
+    end
+
+    context 'locked Delayed::Job' do
+
+      it 'gets destroyed' do
+        # meta :)
+        described_class.delay.cleanup
+
+        # lock job (simluates interrupted scheduler task)
+        locked_job = Delayed::Job.last
+        locked_job.update_attribute(:locked_at, Time.zone.now)
+
+        expect do
+          simulate_threads_call
+        end.to change {
+          Delayed::Job.count
+        }.by(-1)
+      end
+
+      context 'respond to reschedule?' do
+
+        it 'gets rescheduled for positive responses' do
+          SpecSpace::DelayedJobBackend.reschedule = true
+          SpecSpace::DelayedJobBackend.delay.start
+
+          # lock job (simluates interrupted scheduler task)
+          locked_job = Delayed::Job.last
+          locked_job.update_attribute(:locked_at, Time.zone.now)
+
+          expect do
+            simulate_threads_call
+          end.to not_change {
+            Delayed::Job.count
+          }.and change {
+            Delayed::Job.last.locked_at
+          }
+        end
+
+        it 'gets destroyed for negative responses' do
+          SpecSpace::DelayedJobBackend.reschedule = false
+          SpecSpace::DelayedJobBackend.delay.start
+
+          # lock job (simluates interrupted scheduler task)
+          locked_job = Delayed::Job.last
+          locked_job.update_attribute(:locked_at, Time.zone.now)
+
+          expect do
+            simulate_threads_call
+          end.to change {
+            Delayed::Job.count
+          }.by(-1)
+        end
+      end
+    end
+  end
+end