This issue happened to me yesterday, when switching between default user and guest (Access disk of device not starting properly). I did have patchmanager installed, so I haven’t been able to rule that cause out.
What I did find was that when I tried to start Jolla-settings from icon it failed to start. But when starting from terminal it successfully launched, though with warnings that “manager” couldn’t be created (can’t remember the exact wording) and that the database was locked. Will try to recreate the behavior when I have more time.