I started getting these artifacts on my AME exports a few days ago. My videos were coming out fine for about two years and then this suddenly started happening. I'm exporting to H.264 and I have a few Lumetri Color tweaks in Premiere, mainly temperature and curve adjustments. No other manipulations were done to the source footage.
You can see in the clip there are small white and black pixels appearing in the lower right corner of the video.