Ender pearls thrown into end gateways occasionally fail to teleport the player or, when they succeed, occasionally cause very heavy memory usage

In 24w41b, throwing an ender pearl into an end gateway very frequently failed to work correctly. Sometimes it would work fine, sometimes the pearl would be teleported instead of the player, and sometimes the pearl would simply fly through the gateway as if it were air. I opted not to report this until 1.21-pre1 had dropped, and sure enough, things have... mostly, generally, improved in this pre-release. Throwing a pearl into an end gateway now almost always succeeds but, very occasionally, still fails; I haven't been able to repro enough to be able to tell in what way it's failing. A bit more commonly, and perhaps more worryingly, when the teleport succeeds, it will sometimes result in persistently very heavy memory usage which can (in singleplayer at least) bring some aspects of gameplay to a crawl. This is seemingly fixed upon pausing the game.

So all told, I would say the gateway code needs a thorough review and a bit of patching before 1.21 ships, even if the present issues aren't quite world-breaking.

I was unable to capture a recording of the gateway failing to work due to the rarity of that issue, but I did get a couple that show the memory issue. Note that the severity of this bug is highly variable; in the first video my allocation rate peaked at 920 MB/s, but in another instance it was over 1600, and in yet another I neglected to open F3 but chunks were loading at a snail's pace. In the second video the rate shown is quite low but my memory is "flushing" very frequently, leading me to doubt the displayed number, while chunk loading is quite slow at the main island; this has happened on more than one occasion. Also, it should be noted that my hardware is unusually capable at handling tasks requiring large, sustained memory bandwidth; it's possible that a more typical system will fare significantly worse than mine.

To reproduce

In creative mode, open F3 and throw an ender pearl into a naturally generated end gateway. Continue doing this until you notice the bug;(s) you may have to go at it for a minute or two.