x-box live sync issue

My son plays minecraft. He uses the same account on two different x-boxes one at my house and one at his mom's house. For the past few months each time he loads the game at a different house he sees an error message. This says 'my other x-box is taking a long time to sync'. We are then given the option to open the last local copy or to wait. Unfortunately waiting does not help ever. When we select to proceed we lose saved progress from the other x-box.

Can anyone help / advise on this issue please.

:)