Inbox folder to sync disappears on Phone

Have had this happen to 2 users now.

They complain their mail is no longer working on the phone (HTC One)
When you go to the mail account setup on the phone using Exchange Activesync, Folder to Sync "Inbox" is gone and you cannot get it back.

Tried removing one user's GroupWise setup on phone and putting it back - still no luck. Had to remove the user from the Datasync and put the user back into the datasync. Then set the user's phone up to sync again and the inbox is now there.

Has anyone else experienced? Trying to figure out what is causing the Inbox folder to disappear!

DS- Linux, 1.2.4, GW -12sp1 on Linux

Thanks
Christa