Remove Unrelated Content Assets-job fails

For a little over a week has the job "Remove Unrelated Content Assets" failed with error (the job has been set to run once daily):

The jobs seems to end virtually directly when executed.

The DELETE statement conflicted with the REFERENCE constraint "FK_tblContentProperty_tblContent2". The conflict occurred in database "dbEpiCmsSF", table "dbo.tblContentProperty", column 'ContentLink'.

The EPiServerErrors.log contains the following:

2014-08-14 16:35:15,153 [58] ERROR EPiServer.DataAbstraction.ScheduledJob: Job EPiServer.Util.CleanUnusedAssetsFoldersJob failedSystem.Data.SqlClient.SqlException (0x80131904): The DELETE statement conflicted with the REFERENCE constraint "FK_tblContentProperty_tblContent2". The conflict occurred in database "dbEpiCmsSF", table "dbo.tblContentProperty", column 'ContentLink'.  at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)  at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)  at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)  at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)  at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds)  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)  at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)  at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()  at EPiServer.DataAccess.ContentSaveDB.<>c__DisplayClass4.b__3()  at EPiServer.Data.Providers.SqlDatabaseHandler.<>c__DisplayClass4.b__3()  at EPiServer.Data.Providers.SqlDatabaseHandler.<>c__DisplayClass7`1.b__6()  at EPiServer.Data.Providers.SqlTransientErrorsRetryPolicy.Execute[TResult](Func`1 method)  at EPiServer.Core.DefaultContentRepository.Delete(ContentReference contentLink, Boolean forceDelete, AccessLevel access)  at EPiServer.Util.CleanUnusedAssetsFoldersJob.Execute()  at EPiServer.DataAbstraction.ScheduledJob.<>c__DisplayClass9.b__5()ClientConnectionId:e845f241-2acf-46ae-b5ba-250915bcb3e8Error Number:547,State:0,Class:16>>>>

How do I figure out whats wrong?