UE5 output from the Movie Render Queue
What could be causing this problem?
Looks like the result of temporal accumulation. In other words, shadow samples are accumulated over multiple frames in order to get more accurate results. This can cause a difference in sample count for pixels that were occluded in previous frames that will appear as a ghosting effect. The fix will probably be increasing the spacial samples and decreasing the temporal sample accumulation.
This has a heavy performance cost, but for MRQ that’s probably not a problem.