This does not happen in 4.25.4.
It has been confirmed to occur with 4.26.2 and UE4main.
After playback is complete, a large amount of stalls can be seen in Insight.
1. Open NewMap.umap of the attached project.
2. Play in PIE or Standalone.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-117174 in the post.