I was playing Vanilla Minecraft survival, and I went to a portal in the overworld linked to a safe place high up in the Nether enclosed by netherrack blocks. (Completely safe)
But just before the loading screen for entering the nether appeared, the auto-save icon appeared and slowed down the game a lot, and after the saving was done the nether loaded in properly, but suddenly I was swimming in lava, while I should be up high.

Now I lost all of the stuff I worked a long time for, and can't find them back, even in a back-up world in creative. (Because there was some netherite stuff in my inventory)

I really hope this gets fixed soon, so that it won't happen to me and other players anymore.