Error 802 during sync

We have several FileMaker Go apps deployed, both using GoZync. One of the apps continues to sync with our FileMaker Server. However, the other, which has been working correctly for about a month, has started giving Error 802 messages on several but not all of our iPads when attempting to sync. Both apps use the same server and GoZync files.
What things should I start looking at to troubleshoot this problem?
Thanks!
What things should I start looking at to troubleshoot this problem?
Thanks!