When an entity teleports to a player, that entity receives its yaw and pitch rotation data regardless of if they are moving or stationary.
When either a player or entity teleports to a (this is not tested for all) mob or presumably any non-player entity with yaw and pitch values, the rotation data is only copied when the entity being teleported to is in motion. If they are standing still and simply looking around, it's rotation data will not be copied.
As far as I can tell, this seems to be an issue of non-player entity rotation data only being updated when they are in motion. I remember seeing a comment Searge made in another bug thread in which he mentioned that 'mobs don't serialise their orientation':
https://bugs.mojang.com/browse/MC-61587?focusedCommentId=191897&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-191897
Is there potential that this could be the issue?
Edit: u/TimMinChinIsTm-C-N-H from the MinecraftCommands subreddit (http://www.reddit.com/r/MinecraftCommands/comments/2raklr/teleporting_to_mobs_and_other_nonplayer_entities/) correctly mentioned that I should clarify that if you teleport to a non-player entity, the rotation data you receive will be the final rotation when they were last in motion. This is regardless of whether they have since rotated but remained stationary, meaning you can be rotated in a completely random direction unless you teleport as they are moving. Hopefully this better explains the issue at hand.
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kumasasa
Alright, this has been a bug that's been bothering me forever, so I'm going to reply instead of the ticket's creator: Yes, this bug is still happening since then, even now in 1.10.2. Always been there, never fixed, caused tons of issues. Please open this issue.
Since you seem to care more about the ticket then the creator, I changed you to the reporter.
Also, the creators last activity was in januari 2015.
Okay, thanks I guess.
In 1.11 it seems to never change the pitch or yaw of the player even if the entity is moving.
@unknown Did you use /tp or /execute teleport?
If the latter, did you add the ~ ~ for the xy rotation?
(Just checking)
wobst.michael
Is this still an issue in the most recent versions (currently that is 1.13, or the latest snapshot 18w31a) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.
Is this still an issue in the current Minecraft Snapshot 15w46a or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.