GWclient 14.2.1:multi user / column add user access denied

Anybody experiencing the following with the new (rebranded) GW client 14.2.1 re-branded Micro Focus

A couple of users started reporting that either the multi calendar view (which functioned 100% correctly with GW client 14.2.0) crashes, OR that they cannot add more users to their view. Especially in this last situation, and just after upgrading the client to 14.2.1 rebranded:

- co-workers that WERE visible in the multi-calendar view just disappeared
- trying to re-add the co-workers in the multi-calendar view -> user can be selected, but the final check box to (re-)add the coworkers is greyed out. Pressing the OK button will result in an "access denied"

Reverting to the previous 14.2.0 client immediately resolves the problem: all users previously visible in the multi calendar view are immediately visible again, and additional co-workers can be added to the view without error message.