I am also having this problem painting on my Wacom cintiq companion. I used to get it on PS too but they fixed it eventually. I use this type of software almost exclusively for painting so until this gets fixed affinity photo is fairly useless to me because I don't want to be painting in one program and finishing in another when I currently can do it all in PS. 50% hardness still looks horrible on a A4 300 dpi canvas. Fix it and I could consider affinity as an alternative because I'm not a fan of app subscription. Top half is drawn full screen, bottom half drawn while zoomed in is ok but I like to work out my ideas full screen.
Mariano Iannelli reacted to Angie M A in Disappointing experiences with Brush Tool