Any ideas how an error like this might occur? It sometimes occurs in a production log file, when a user is logged in and uploading files (entity ECLFile, which is a specialization of FileDocument). The users don't report problems, but I am curious as to how this can occur, and how we can avoid it. 2014-06-05 08:14:04.050 ERROR - Connector: com.mendix.core.CoreRuntimeException: com.mendix.core.CoreRuntimeException: Exception occurred in action '{"ids":[{"guid":36028797018964910,"entityId":128,"objectTypeHash":128,"objectType":"ECL.ECLFile"}],"type":"RetrieveIdListAction"}', all database changes executed by this action were rolled back