The bug

When using the /tp command to change an entity's rotation, it always succeeds server-side, but sometimes the mob does not update client side and continues facing in the old (wrong) direction, resulting in a desync.

How to reproduce

1. Download and open the attached world. It contains five armor stands, and five skeletons with all behaviors disabled. A line of fire indicates which way the mobs are facing server-side.
2. Press the button on the command block. This rotates all the mobs by 90 degrees with a teleport command.

Expected behavior
All the mobs should spin 90 degrees to match their server-side rotation as indicated by the flames.

Observed behavior
The armor stands rotate as intended, but the skeletons continue looking straight on. The flame particles indicate they were correctly rotated server-side, but not client side. If you push the button again, or punch the skeleton, it will usually correct itself.