Animations are stuttering in Game Preview Server window

When 'Run Dedicated Server' is unchecked and you run PIE with 2 or more clients, all client's animations are stuttering on Game Preview Server window. This does not happen when Run Dedicated Server is checked.

This was working as intended in 4.19.2 (CL-4033788). This was reported and tested in 4.20 (CL-4212847) and reproduced in Main 4.21 (CL-4234136).

1. Open the UE4 Editor and create a new Third Person Template project
2. Set Number of Players to 2 or higher
3. If Run Dedicated Server is checked, uncheck it
4. Set Play Mode to New Editor Window (PIE)
5. Press Play

Results: All animations are stuttering and lagging only for the server side.
In client windows there is no such problem.

Expected: Animations are expected to work smoothly for server and client's side