Exported frame randomly pixelated
When I use the "Export Frame" feature in the timeline (Shift + E), whether I export JPEG or PNG or TIFF, the same image will randomly be rendered in a poor/pixelated quality, and sometimes rendered properly.
For example the image below was me exporting that frame twice in a row:


Zoomed in to see better on the forum:


I exported it 6 times, it went like this: bad, good, good, bad, bad, bad (the images above are the 2 first).
This have been consistently happening on all my projects for the past couple of months.
I use proxies, and I tried exporting the frame with them on/off and this doesn't make a difference.
Any idea what could be causing that and how to fix it? Thanks!
Using Premiere 14.4.0 on macOS 10.15.7.
