When you are loading up a world your character spawns in the world before all the assets are loaded making it so you be killed by enemies before you can even see the world around you

When you load a world your character spawns before the assets and blocks load making it so when you spawn you could have been killed and lost all your items. For example I just started up my world on the nether update and and went exploring. I logged out in the nether and when I came back I was knocked into lava by a magma cube. It's a frustrating bug and I hope it gets fixed soon