When I try and add a stroke to a circle with a brush texture instead of a simple line, I always have this issue where it does not connect properly. I tried converting the ellipse to curves and I've tried many different brushes, none of this worked. It only works when a use a simple line as a stroke. I am having this issue in Affinity Design. I'm not sure if it is a problem in Affinity Photo. You can see at the top of the circle where this happens.