Syncing of System Groups to PAB Groups

Hi Forum,

I'm experiencing the problem that system groups inherited in personal groups don't get updated.
In Detail:
User A has book called "acme". This book has a group called "incident". This Group inherits some groupwise users, some users of the PAB and some groupwise system groups.
I updated one of the system groups, e.g. delete some addresses and add some others.
Some Days later User A reports that the groupwise group in his personal personal group "incident" misses this changes.
I deleted the system group from the "incident" group and added it again to fix this.
Unfortunately this seems not to be a single failure. The system group never gets updated after changes.

I have to mention that User A is a proxy account, only used via proxy access. It is very rare that a client log in with User A.

Any suggestion how to solve this or is this "works as designed"?