Since the hardware seems to be sending the correct data, this looks to me like this is a software issue.

I noticed a couple of times that control data from my yoke doesnt get picked up correctly by FS2020, but before it were glitches, only now the ailerons seem stuck. When I move left or right, the yoke in the cockpit doesnt respond at all, while it responds perfectly fine to pitch input (also buttons on the yoke work fine), only when I turn the yoke close to max, the aircraft jerks onto a steep bank. When checking the connection to FSUIPC, everything seems fine and every small input is registered over the complete range of motion, so it doesnt seem to be the yoke, there's something going wrong in the connection between FSUIPC and FS2020.

Is there someone who knows what this might be, or even better, how to fix this?

Obvious questions seems to be whether you see the problem when you set up the yoke directly in MSFS rather than going through FSUIPC.
If you don't it would seem pretty clear the problem lies somewhere between those two.

Sounds like there's very likely another device making inputs to the roll axis, which intermittently conflicts with the intended control axis inputs.

Check every input device attached to the computer, including game controllers and devices that wouldn't make sense to have an aileron input (e.g. rudder pedals).

Also, I recently had an issue where I was getting phantom inputs from a device assignment that had long-before been removed.  The control profile was blank (I use FSUIPC for control axis assignments), but cycling the control profiles in the controls menu to default and then back to my custom (blank) profile brought several old assignments back into visibility.  I suspect it was an unwanted spurious restoration of a profile previously stored in the cloud.