Follow-up
Where are your profiles stored? Are they by any chance in the program folder (thus, common to all users)? Because the only other thing we can think of is that on start-up / profile loading, the Group INI entry is cross-checked against the actual profile-name INI(s). If one INI is locked (maybe because 'profile in use' in another instance of Pro), it could cause Pro to think that profile is corrupt and kick it out of the Group. If it always seems to happen to the same profile/s, that's a strong indicator if your set-up is such that dual-use of a shared profile is possible/likely
EDIT: another thing to check is that you don't have that profile still Scheduled individually as well as Scheduled c/o the Group...
Where are your profiles stored? Are they by any chance in the program folder (thus, common to all users)? Because the only other thing we can think of is that on start-up / profile loading, the Group INI entry is cross-checked against the actual profile-name INI(s). If one INI is locked (maybe because 'profile in use' in another instance of Pro), it could cause Pro to think that profile is corrupt and kick it out of the Group. If it always seems to happen to the same profile/s, that's a strong indicator if your set-up is such that dual-use of a shared profile is possible/likely
EDIT: another thing to check is that you don't have that profile still Scheduled individually as well as Scheduled c/o the Group...