Seems like the same basic issue they were having
- Temporal AA: ✓
- Temporal dithering: ✓
- crazy flashing shadows coming from the object that was being dithered: ✓
I noticed the flashing shadows also stopped if I removed the temporal dithering from the material the object was using. Or if I turned off Temporal AA altogether the problem resolved as well. But neither of those are actual solutions.
I really wish there was some documentation of these Dynamic Inset shadow and Light attachment as group. I only learned that this fixed the issue by trying out different options one by one in the editor until I saw the issue resolved. Once I realized they fixed the issue, I searched as much as I could to learn what they are, but there wasn’t anything I could find.