If you want to spawn a rotated Zombie you can do so by:
/summon Zombie ~ ~1 ~ {Rotation:[90f],Motion:[0.04]}
If you do the same thing with a Slime:
/summon Slime ~ ~1 ~ {Rotation:[90f],Motion:[0.04],Size:1}
It does not work.
This issue persists even if you make a Slime ride something. If you summon a Slime riding a Zombie, the Slime will adhere to the Zombies rotation up to +-45° approximately. When the Zombie rotates more, Slime will no longer adhere to Zombie rotation.
Comments 3
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.
Can confirm, even tried to spawn with NoAI tag, but slime faces always south when spawning