Everything in render distance deletes itself

I was working on a minigame project for me and my friends and I left the world to go make a texture pack for the world to make it look nice, and when I came back everything in my render distance was replaced by a big hole into the void. This was on a superflat world with trusted addons and some made by me on a trusted site. None of my home made mods or the addon I used have ever caused and issue so can you look into it so I don't loose my worlds again? Also this only happened after I updated to 1.17.30. Thanks.