I am also having this issue - I never really dabbled in Pets, just used premades, but I just got Horse Ranch and wanted to make a custom painted horse to match the one we used to have IRL, and when I exited paint mode, I was also getting these seams, as well as any painting I did having artifacting/low res appearances.
I have no mods installed (removed while I work on updating them for this expansion, I haven't played in a few months). I did a graphics card driver update so that is all up to date, did a full restart of my computer, game, etc. The issue happened both before and after the graphics card update, so that doesn't appear to be the issue.
I really hope this gets fixed, bc if not, having the Paint Mode option is useless.
How the hell is a decently important issue of a 40 euro dlc being ignore since 2019 (specially when apparently this issue started happening after a certain update according to one of the comments here)
