Half of my custom entities are invisible/not spawning

I know this post came up a lot, but none of them really fit to what I was experiencing. My mobs were all there and fine and dandy, then suddenly just a couple days before the 2020.3 update, half of them became invisible, and one of them would not spawn in at all. I tried to give them new skins, and that didn't work. I deleted them and remade them, and changed the skins, but that did not work either. I fiddled around, and eventually came across one similarity: they all had a simple despawning procedure (except the one that wouldn't spawn at all, probably a different issue altogether). The procedure is an if/else statement with: if is day in provided world, do despawn provided entity (which did turn into despawn event/targeted entity after the update). I don't know how to provide pictures, but if you could tell me I will provide any necessary images. TIA