This issue was reported by a licensee and we also hit it during dev work on the crowds demo. It seems that this may be a general issue with motion vectors and teleporting actors as there are various threads on EDC that seem related.
Steps to Reproduce
Open the MetaHumanCrowdSample project
Select the PostProcessVoume in the Plaza level
Set Amount to 0.5 and Max to 5
PIE
Fly the camera through the crowd
Note the occasional motion blur artifacting on the characters nearest to the camera
Have Comments or More Details?
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-395897 in the post.