Default [Q] 4.4.4 Exchange Calender Sync Issue

Hi guys. My father in law is having issues with syncing his Exchange calender with his Nexus 7. It was working fine before the last OTA, but since updating to 4.4.4 the calender won't sync. He has a Nexus 7 2013 wifi running stock 4.4.4 with a locked bootloader and non-rooted device. He is still getting emails, which seems odd. Both calender and email are set to sync at 15min intervals. He has already tried deleting the account and reinstalling it. This solved the problem briefly, but shortly afterwards the calender sync issue came back.

Any help would be appreciated. Thanks.