In some environments the Model.reset_column_information is not reflected to threads. So an import error message appears. Reset needed model column information for each thread.

lib/import/otrs.rb

@@ -83,6 +83,11 @@ module Import
 
         threads[thread] = Thread.new {
 
+          # In some environments the Model.reset_column_information
+          # is not reflected to threads. So an import error message appears.
+          # Reset needed model column information for each thread.
+          reset_database_information
+
           Thread.current[:thread_no]  = thread
           Thread.current[:loop_count] = 0
 
@@ -163,5 +168,9 @@ module Import
     def customer_user
       limit_import('CustomerUser', limit: 50)
     end
+
+    def reset_database_information
+      ::Ticket.reset_column_information
+    end
   end
 end