I am really sorry if this a duplicate

1. When you summon a mob (e.g. zombie):
The zombie rotates a little bit after summoning it (see attached movie)

2. When you teleport a mob to a player (e.g. zombie to @p):
The zombie rotates about 2.5 seconds after the teleport
But what is really strange: Even the "blue line" points in the wrong direction, but when you spectate it, you look in the correct direction

Might relate to MC-46647