in case the error message continues with something similar to
Caused by: com.mendix.systemwideinterfaces.MendixRuntimeException: Autocommitted objects
you have to make sure that you commit all (related) objects.
An Autocommit happens when you commit an OrderLine that is related to an uncommited Order. The Order would be Autocommitted.
Check if the object you are trying to sync still exists on the server. Sync errors often show up when you make changes to an object locally when the object is already deleted on the server. When the sync process tries to update the server object it will come up empty, thus causing the error. Using a ‘soft delete’ is recommended for these situations to remove the object from the device before it is deleted from the server.