I had the same problem since the 3-4-2. I had reverted to 3-4-1 and all was back OK.
But I decided today to figure this out since there was a newer version 3-4-3 but same issues.
After many hours of searching I found that having 2 monitors was my issue for me.
If I put the viewer on the main monitor, then rebaked, all was OK but if I slid the Viewer on my second monitor, then it was all fuzzy and messed up.
Not sure on my end what I can do to get my second monitor to be OK again but for now I use my main monitor if I need to rebake.
Ginger