Vanilla Minecraft, no mods, no shaders, etc.

I play a singleplayer game started with version 21w38a, the problem wasn't as heavy then (just some lagging), became much worse after updating to 21w39a.

When I search for loot in chests underwater (shipwrecks or underwater ruins), the game gets heavily lagged/freezes and then crashes. Average memory use under game is 65%, gets to 100% when trying to open a new underwater chest, even in previously loaded chunks, close to base. Feels like something happens when the game wants to create the loot.

Doesn't happen when looking in underwater chests that have been opened before, or chests above water.

Issue repeats when reloading the game, and also after updating Windows.

Thanks for your time.