No, I don't use automatic profile switching.
I highly suspect some more or less recent Win10 update. But it's hard to tell.
My virus scanner didn't find anything suspicious. Also, it's always active.
If it's an update issue with Win 10 (or some .NET update maybe???) , I should probably not be the only one to have this problem.
I mean, I have that workaround, but I will continue trying to solve this, as it's pretty annoying.
UPDATE:
Solved it! (kinda)
I started the program explicitly as "Administrator" and BOOM! Profile switching started to work.
The funny (or weird) part is: I already told Windowes to always start this program as Administrator shortly after installing it. But Windows somehow must have "forgotton" this, despite the fact that the option was still ticked in the "Compatibility" tab of the .exe file preference.
So, explicitly starting it as admin once, somehow fixed it. I can now sart it normally via my existing start menu link and it still works.
Maybe this is helpful for other who may expierience this.