I have this same problem, I have gone through it again and again. Sadly, there's no real guaranteed way to fix it. After a while, I just stopped noticing them, really. They only appear in a few areas such as those walls in the screenshot, around the borders of some vistani caravans, and the large campfire pits in the mistcamp and vallaki vistani camp. I also have the text bar at the bottom where you write your emotes will flicker in and out of existence if something isn't highlighted.
Hopefully Windows 10 might fix it, but I've found no clear solution, but you're not alone.