Chunks and worlds have problem loading in new snapshots

Minecraft's new snapshots have problems in loading worlds and chunks!

i think it may occur only on older pc's but i heard my friend is having problems too.

just when you load new world you need to wait 5-10 minutes to load world then the same with chunks!

Also it takes ages to boot up the game with that version

Seed: -63901196999178774369

also some structures are floating like a grass that is spawning on water or in air