Infrequently we observed permissions getting revoked (untick) automatically when we click on the Save button in Assign Roles. 

Lately we were adding new user in Item roles and on hitting save we observed all users who had access to specific role, lost access to that role (not all roles). Have attached screenshot of short snippet comparison between config.xml before the activity(on the left in red) and after the activity(on the right in green). The two roles in the screenshot were not touched during the activity and yet access was lost.

Kindly help with this issue.