Thanks, Ron and Michail.
I suspected already windows ink may have something to do with it and had disabled the options in the pen control panel. I disabled windows ink now completely in the local group policy editor and restarted the PC. Unfortunately it still does not work. I then disabled the app suggestions in the policy editor as well, but still the same. I checked again both settings are disabled indeed, but strangely the windows ink workspace in the toolbar is still visible and still works. I fiddled around again with the pen control panel settings, but nothing works. I need to mention I had no problem before the 1.8 update, so it seems related to a change that was made in Affinity Photo. Still, I hope Wacom tablet users can fix the issue by deactivating windows ink.