In the case the entity is rotating but not moving, its horizontal rotation values won't be updated. So it is not possible to detect entities while they're standing still or while they're riding a minecart.
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galaxy_2alex
Ticket resolved as incomplete, because no answer in a reasonable amount of time (1+ year), if it still happens, please update the ticket.
This still happens in 1.12.2 and the latest 1.13 snapshot as of writing (17w50a). I'll try to elaborate on what the OP was likely trying to say; here's a quote of mine from a recent different rotation report someone made (MC-121855):
Also, when not pathfinding, their horizontal rotation data freezes in the direction they were last moving, and doesn't update at all when looking around/at the player while in idle mode. Their vertical rotation updates normally though.
In other words, things like mob detection commands which may rely on their horizontal rotation (such as a randomizer perhaps) won't work, even if they visually turned in the proper direction. Their actual horizontal rotation is based on the last direction they were moving in (or are attempting to move in, such as when they're immobilized from mounting something). You can tell that their rotation is off if you try to update any of their nbt tags, or teleport them, or simply nudge them yourself. They'll snap straight to their actual horizontal rotation with any of those methods. Rotating them with commands updates their rotation values accordingly though.
Speaking of teleporting, it can be a bit buggy when trying to change NoAI:0 mobs' direction with it, especially with 180ish° rotations, but it's purely visual bugs in this case (I wonder what kinds of uses there'd be for manually rotating a NoAI:0 mob anyway haha). And for NoAI:1 mobs with a passenger, unless you shift the tp coordinates slightly too, they visually won't turn their bodies (you'll see the head turn though)... but I'm getting into a whole 'nother bug now so I'll stop here.
endsky
Confirmed for 1.19.4
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.