I'm getting some weird artifacts when using the pen tool. You can see it right at the beginning of the attached video. After that I can continue to work as intended. This bug seems to appear randomly and I encountered it just today. I'm working on an Ipad pro M1 2021, the Wifi 500gb 8GB Ram Version. Ipad OS is 15.5 and therefore currently up to date. The video shows the artifact even after I restarted the Ipad to try if the artifacting goes away.
And overall the performance, especially when drawing with some brushes, seems to be worse than on my old Ipad Air 2019 that I have been using before the Ipad Pro. Maybe it's the IpadOS 15.5 Update that's causing all this stuff. On the other hand my other apps seem to work fine.