Single group keeps disappearing from client

Our users are experiancing an issue with AD integrated groups disappearing from the Spark client. It shows up again once they relogin so they’re sedated but we’re unable to figure out the root cause of the problem. Does anyone have any insight into this issue? Users are using version 2.6.3 on Windows 7&8.

If you are using Openfire 3.9.3, maybe this one OF-830