Download the log from your app or watch the live log for more information regarding the generic Mendix error. If you run it locally you can also check the error within the console of Mendix Studio Pro. If I understand correctly, the 560 error is received by the external db. In that case the above error is causing that issue due some logic seems not to be working accordingly and breaking off the action. In most cases the generic mendix error is caused due lack of error handling.
You can also check out this learning path about Error handling