I've just updated Affinity Photo to version 1.8.0.585 and I am experiencing the same exact problem as Pluscuamperfecto. I use Affinity Photo for painting myself, and found that with the new update, the brush stroke freezes for a half of second, and then continues with the brush stroke. I have experienced something similar in the past, and found that Windows Ink was the culprit. I tried disabling it this time, and the "freeze" goes away, but of course pen pressure goes away as well.
Also when Windows Ink is enabled, it frequently causes me to draw only straight lines.
Hoping to find a way to fix this. I can deal with it, but it is mildly frustrating.
Thank you for the help!