When I loaded up my old world after updating to 1.19.20 multiple chunks would be transparent. The blocks would still be there but transparent. I even tried older backups and the same chunks would not work. If I save and quit in one of those chunks it will load but different ones will break.

See screenshots

I also had a public world download that worked before the update, see if the world works for you. CowCrafters 2nd Survival World 8/7/22 Update Minecraft Map (planetminecraft.com)

Ive been playing this world for 1 year + and its really annoying