Don't know if this is helpful. I've had no problems with Affinity 1.9 until today, and today was the first time for me to use my graphics pen with Affinity Photo. My editing is usually minimal and I have been using Affinity a lot recently, but today I wanted to go in on some fine detail to do changes and my pen sent the whole thing odd. Zooming using the pen sent the display crazy, and trying to do a selection just hangs Affinity.
I'm currently looking to see if I can get updated drivers for my pen/ graphics tablet, but it seems to work ok when navigating menus, or if I use it outside of Affinity.