Mobs and Entities Despawn upon opening world

Upon opening my world, all of my hundreds of paintings for decoration were gone, along with 20 or so armor stands and the armor on them, which included enchanted chain mail and iron armor, and four sets of fully enchanted netherite armor with all the enchantments attainable in game. My Villager breeder and villager marketplace was empty, with all them gone. My 12 skeleton horses were also gone from my stables. My cows and sheep despawned as well. Even the mobs (parrots, villagers, fish, horses and skeleton horses) I had nametagged despawned. As far as I can tell this has only happened in the rough radius of my castle, with the chunks farther out being unaffected, my beacon a couple chunks away was not affected. Also it only seemed to affect mobs, armor stands, and paintings, with item frames, banners, and mob heads not being affected. Overall I'm not very happy with this, as I lost hours upon hours of progress. I tried using my backup through Nintendo online, but whenever I opened the world the same issue occurred. (Which makes me think it might be an issue with saving the world) I have some photos of my world below, with some of them being before and after, as well as what the menu screen shows, and a comparison of what the room was really like when I logged in.