diff --git a/app/controllers/application_controller/handles_errors.rb b/app/controllers/application_controller/handles_errors.rb
index 819af4c88..ca8f8bf5d 100644
--- a/app/controllers/application_controller/handles_errors.rb
+++ b/app/controllers/application_controller/handles_errors.rb
@@ -32,7 +32,7 @@ module ApplicationController::HandlesErrors
   end
 
   def unauthorized(e)
-    error = humanize_error(e.message)
+    error = humanize_error(e)
     response.headers['X-Failure'] = error.fetch(:error_human, error[:error])
     respond_to_exception(e, :unauthorized)
     http_log
@@ -44,9 +44,9 @@ module ApplicationController::HandlesErrors
     status_code = Rack::Utils.status_code(status)
 
     respond_to do |format|
-      format.json { render json: humanize_error(e.message), status: status }
+      format.json { render json: humanize_error(e), status: status }
       format.any do
-        errors = humanize_error(e.message)
+        errors = humanize_error(e)
         @exception = e
         @message = errors[:error_human] || errors[:error] || param[:message]
         @traceback = !Rails.env.production?
@@ -56,38 +56,39 @@ module ApplicationController::HandlesErrors
     end
   end
 
-  def humanize_error(error)
+  def humanize_error(e)
+
     data = {
-      error: error
+      error: e.message
     }
 
-    case error
-    when /Validation failed: (.+?)(,|$)/i
+    if e.message =~ /Validation failed: (.+?)(,|$)/i
       data[:error_human] = $1
-    when /(already exists|duplicate key|duplicate entry)/i
+    elsif e.message.match?(/(already exists|duplicate key|duplicate entry)/i)
       data[:error_human] = 'Object already exists!'
-    when /null value in column "(.+?)" violates not-null constraint/i
+    elsif e.message =~ /null value in column "(.+?)" violates not-null constraint/i
       data[:error_human] = "Attribute '#{$1}' required!"
-    when /Field '(.+?)' doesn't have a default value/i
+    elsif e.message =~ /Field '(.+?)' doesn't have a default value/i
       data[:error_human] = "Attribute '#{$1}' required!"
-    when 'Exceptions::NotAuthorized'
+    elsif e.message == 'Exceptions::NotAuthorized'
       data[:error]       = 'Not authorized'
       data[:error_human] = data[:error]
+    elsif [ActionController::RoutingError, ActiveRecord::RecordNotFound, Exceptions::UnprocessableEntity, Exceptions::NotAuthorized].include?(e.class)
+      data[:error_human] = data[:error]
     end
 
-    if Rails.env.production?
-      if data[:error_human].present?
-        data[:error] = data.delete(:error_human)
-      else
-        # We want to avoid leaking of internal information but also want the user
-        # to give the administrator a reference to find the cause of the error.
-        # Therefore we generate a one time unique error ID that can be used to
-        # search the logs and find the actual error message.
-        error_code_prefix = "Error ID #{SecureRandom.urlsafe_base64(6)}:"
-        Rails.logger.error "#{error_code_prefix} #{data[:error]}"
-        data[:error] = "#{error_code_prefix} Please contact your administrator."
-      end
+    if data[:error_human].present?
+      data[:error] = data[:error_human]
+    elsif !current_user&.permissions?('admin')
+      # We want to avoid leaking of internal information but also want the user
+      # to give the administrator a reference to find the cause of the error.
+      # Therefore we generate a one time unique error ID that can be used to
+      # search the logs and find the actual error message.
+      error_code_prefix = "Error ID #{SecureRandom.urlsafe_base64(6)}:"
+      Rails.logger.error "#{error_code_prefix} #{data[:error]}"
+      data[:error] = "#{error_code_prefix} Please contact your administrator."
     end
+
     data
   end
 end
diff --git a/app/models/application_model/can_associations.rb b/app/models/application_model/can_associations.rb
index 0cb97fde8..4aaa724fb 100644
--- a/app/models/application_model/can_associations.rb
+++ b/app/models/application_model/can_associations.rb
@@ -51,7 +51,7 @@ returns
 
         # complain if we found no reference
         if !lookup
-          raise ArgumentError, "No value found for '#{assoc_name}' with id #{item_id.inspect}"
+          raise Exceptions::UnprocessableEntity, "No value found for '#{assoc_name}' with id #{item_id.inspect}"
         end
 
         list.push item_id
@@ -94,7 +94,7 @@ returns
 
         # complain if we found no reference
         if !lookup
-          raise ArgumentError, "No lookup value found for '#{assoc_name}': #{value.inspect}"
+          raise Exceptions::UnprocessableEntity, "No lookup value found for '#{assoc_name}': #{value.inspect}"
         end
 
         list.push lookup.id
@@ -363,7 +363,7 @@ returns
           lookup = nil
           if class_object == User
             if !value.instance_of?(String)
-              raise ArgumentError, "String is needed as ref value #{value.inspect} for '#{assoc_name}'"
+              raise Exceptions::UnprocessableEntity, "String is needed as ref value #{value.inspect} for '#{assoc_name}'"
             end
 
             if !lookup
@@ -378,7 +378,7 @@ returns
 
           # complain if we found no reference
           if !lookup
-            raise ArgumentError, "No lookup value found for '#{assoc_name}': #{value.inspect}"
+            raise Exceptions::UnprocessableEntity, "No lookup value found for '#{assoc_name}': #{value.inspect}"
           end
 
           # release data value
@@ -408,7 +408,7 @@ returns
           lookup = nil
           if class_object == User
             if !item.instance_of?(String)
-              raise ArgumentError, "String is needed in array ref as ref value #{value.inspect} for '#{assoc_name}'"
+              raise Exceptions::UnprocessableEntity, "String is needed in array ref as ref value #{value.inspect} for '#{assoc_name}'"
             end
 
             if !lookup
@@ -423,7 +423,7 @@ returns
 
           # complain if we found no reference
           if !lookup
-            raise ArgumentError, "No lookup value found for '#{assoc_name}': #{item.inspect}"
+            raise Exceptions::UnprocessableEntity, "No lookup value found for '#{assoc_name}': #{item.inspect}"
           end
 
           lookup_ids.push lookup.id
diff --git a/app/models/application_model/can_cleanup_param.rb b/app/models/application_model/can_cleanup_param.rb
index 778c64140..b900d87e5 100644
--- a/app/models/application_model/can_cleanup_param.rb
+++ b/app/models/application_model/can_cleanup_param.rb
@@ -28,7 +28,7 @@ returns
       end
 
       if params.nil?
-        raise ArgumentError, "No params for #{self}!"
+        raise Exceptions::UnprocessableEntity, "No params for #{self}!"
       end
 
       # cleanup each member of array
@@ -61,7 +61,7 @@ returns
           next if data[name].blank?
           next if assoc.klass.lookup(id: data[name])
 
-          raise ArgumentError, "Invalid value for param '#{name}': #{data[name].inspect}"
+          raise Exceptions::UnprocessableEntity, "Invalid value for param '#{name}': #{data[name].inspect}"
         end
         clean_params[attribute] = data[attribute]
       end
diff --git a/spec/requests/error_spec.rb b/spec/requests/error_spec.rb
index b58f03733..e721cc277 100644
--- a/spec/requests/error_spec.rb
+++ b/spec/requests/error_spec.rb
@@ -13,7 +13,7 @@ RSpec.describe 'Error handling', type: :request do
       # a random error code that can be easily found in the logs by an
       # administrator. However, this makes it hard to check for the exact error
       # message. Therefore we only check for the substring in this particular case
-      if message == 'Please contact your administrator'
+      if message == 'Please contact your administrator' || message == 'Mysql2::Error' || message == 'PG::ForeignKeyViolation'
         expect(json_response['error']).to include(message)
       else
         expect(json_response['error']).to eq(message)
@@ -33,34 +33,50 @@ RSpec.describe 'Error handling', type: :request do
 
   context 'error with confidential message is raised' do
 
-    let(:admin_user) { create(:admin_user, groups: Group.all) }
     let!(:ticket) { create(:ticket) }
     let(:invalid_group_id) { 99_999 }
-    let(:message) { 'Please contact your administrator' }
     let(:http_status) { :unprocessable_entity }
 
     before do
-      # fake production ENV to enable error hiding
-      env = double(
-        production?:  true,
-        test?:        false,
-        development?: false
-      )
-      allow(::Rails).to receive(:env).and_return(env)
-
-      authenticated_as(admin_user)
+      authenticated_as(requesting_user)
       put "/api/v1/tickets/#{ticket.id}?all=true", params: { group_id: invalid_group_id }, as: as
     end
 
-    context 'requesting JSON' do
-      include_examples 'JSON response format'
+    context 'agent user' do
+      let(:requesting_user) { create(:agent_user, groups: Group.all) }
+      let(:message) { 'Please contact your administrator' }
+
+      context 'requesting JSON' do
+        include_examples 'JSON response format'
+      end
+
+      context 'requesting HTML' do
+        let(:title) { '422: Unprocessable Entity' }
+        let(:headline) { '422: The change you wanted was rejected.' }
+
+        include_examples 'HTML response format'
+      end
     end
 
-    context 'requesting HTML' do
-      let(:title) { '422: Unprocessable Entity' }
-      let(:headline) { '422: The change you wanted was rejected.' }
+    context 'admin user' do
+      let(:requesting_user) { create(:admin_user, groups: Group.all) }
 
-      include_examples 'HTML response format'
+      if ActiveRecord::Base.connection_config[:adapter] == 'mysql2'
+        let(:message) { 'Mysql2::Error' }
+      else
+        let(:message) { 'PG::ForeignKeyViolation' }
+      end
+
+      context 'requesting JSON' do
+        include_examples 'JSON response format'
+      end
+
+      context 'requesting HTML' do
+        let(:title) { '422: Unprocessable Entity' }
+        let(:headline) { '422: The change you wanted was rejected.' }
+
+        include_examples 'HTML response format'
+      end
     end
   end
 
@@ -112,12 +128,12 @@ RSpec.describe 'Error handling', type: :request do
       get '/tests/raised_exception', params: { exception: exception.name, message: message }, as: as
     end
 
-    shared_examples 'handles exception' do |exception, http_status, title, headline|
+    shared_examples 'exception check' do |message, exception, http_status, title, headline|
 
       context "#{exception} is raised" do
         let(:exception) { exception }
         let(:http_status) { http_status }
-        let(:message) { 'some error message' }
+        let(:message) { message }
 
         context 'requesting JSON' do
           include_examples 'JSON response format'
@@ -132,10 +148,18 @@ RSpec.describe 'Error handling', type: :request do
       end
     end
 
-    include_examples 'handles exception', ActiveRecord::RecordNotFound, :not_found, '404: Not Found', '404: Requested resource was not found'
+    shared_examples 'handles exception' do |exception, http_status, title, headline|
+      include_examples 'exception check', 'some error message', exception, http_status, title, headline
+    end
+
+    shared_examples 'masks exception' do |exception, http_status, title, headline|
+      include_examples 'exception check', 'Please contact your administrator', exception, http_status, title, headline
+    end
+
     include_examples 'handles exception', Exceptions::NotAuthorized, :unauthorized, '401: Unauthorized', '401: Unauthorized'
+    include_examples 'handles exception', ActiveRecord::RecordNotFound, :not_found, '404: Not Found', '404: Requested resource was not found'
     include_examples 'handles exception', Exceptions::UnprocessableEntity, :unprocessable_entity, '422: Unprocessable Entity', '422: The change you wanted was rejected.'
-    include_examples 'handles exception', ArgumentError, :unprocessable_entity, '422: Unprocessable Entity', '422: The change you wanted was rejected.'
-    include_examples 'handles exception', StandardError, :internal_server_error, '500: Something went wrong', "500: We're sorry, but something went wrong."
+    include_examples 'masks exception', ArgumentError, :unprocessable_entity, '422: Unprocessable Entity', '422: The change you wanted was rejected.'
+    include_examples 'masks exception', StandardError, :internal_server_error, '500: Something went wrong', "500: We're sorry, but something went wrong."
   end
 end