What I expected to happen was...:
Time would run smoothly like with a singleplayer world.

What actually happened was...:
Time seems to stutter back every few seconds, effecting mob movement and elytra, making it impossible to fly without the elytra suddenly losing its momentum and ending up where you were a few seconds ago. Happens primarily on my friend's multiplayer server.

Steps to Reproduce:
1. Go into a whitelisted Multiplayer server.
2. Try to fly anywhere.