My friends and I were playing on a small server we were running. We decided to travel to the end after having previously gone there multiple times, and one of them was teleported almost 3000 blocks away from us. They said their screen turned a greenish colour and then then started to suffocate and started to mine but they kept dying, so they opted to screenshot their coordinates and wait for us to get to them. They were at Y 33, so they were not in the void. They could mine but not move, and they had some valuables with them so we decided to find them. Once we got there, we found the largest end city we had come upon yet, and we found that they have definitely mined around them. We mined some extra, and they rejoined and were fine.

If this had happened on a singleplayer world they would have been screwed, and while I can't jump on the server right now to check my friend said that it might be the same coordinates as the overworld portal. This was the only account I could find (in a short time, I don't have too much time atm) that talks about this specifically: https://www.minecraftforum.net/forums/support/server-support-and/2970066-ender-portal-teleports-to-wrong-location and one on here that was similar but not quite the same (and resolved): MC-90036.

The attachment is the screenshot we took.