Some RDM clients cannot use offline mode

We are experiencing a problem where some clients cannot work in offline mode. Others behave as expected when trying to reproduce the problem internally.

Client version: 13.5.6.0 (enterprise edition)
Server version: 5.0.2.0

Symptoms:

User can start in online mode just fine.
When user switches to offline mode, a login prompt is displayed, only allowing a password to be entered (no username). Expected behaviour is that the treeview remains available and user can continue working.
When starting offline, again the same prompt is shown, only allowing a password to be entered (no username).

As a work-around we have asked users whom are affected by these symptoms to check off the "always prompt for a username" in the datasource connections settings, and fill in their username there instead. This allows them to continue working in offline mode.

Settings have been checked between users who are and who are not experiencing this problem, but no differences where found. The users affected by this problem, also had this problem before we (recently) updated to 13.5.6.0. This problem has not been introduced to new users since upgrading to 13.5.6.0.

Could this be due to some residue of their old installation that needs to be manually cleaned after uninstalling / reinstalling / updating the client? (e.g. registry setting, or some locally cached files?). In order to rule that out, I would like to know how to completely eradicate any trace of RDM ever being on their workstations, and use a realy clean install.


Please advise on how to proceed.