Project templates revert to previous config after Windows reboot

So, when doing the initial configuration of Studio after a recent OS reinstall (or rather PC swap, but let's keep it simple), I messed around with the project template files in the SDL directory, trying to copy my backed up templates from the former PC. I can't tell you now what I did and did not exactly as I encountered some complications and can't really trace back all the hassle I engaged in, but the bottom line now is that I see the templates revert to a previous situation after every Windows reboot, meaning: I recently configured (again) two templates by editing the default one and creating a new one from scratch, then rebooted the PC and what I'm seeing now is one of my templates safely in place, and the default template having reverted to its default setting.

Sorry if my explanation is a bit messy, I hope you get the general idea. The thing is: I could try repairing or reinstalling Studio (though I surely would prefer avoiding wasting time on that), but I'm not sure if it will even help as reinstalls often tend to preserve the "soft" configuration files of users, such as templates, keyboard shortcuts etc.

Another thing I noticed after installing Studio on my PC was that the initial configuration ("Welcome" or whatever) window came up about three times, which is obviously erroneous. So it looks a bit like my copy of Studio for some reason has problems with embedding itself properly into the Windows registry or something.

Any ideas? I'm super tired of reconfiguring my templates all the time.