Armour stands, paintings and NPCs despawn

So, I have a world with quite a lot of armour stands, and before this I have had no problems with them, until now. For whatever reason, my armour stands randomly disappeared yesterday. I checked across my entire world and only a handful were in the same spot as usual.

this made me very upset and I decided to try to teleport all armour stands to me. Some deleted armour stands held tridents, and when I teleported all entities to me, I saw tridents.

I don't know how this is happening, but from my knowledge, it seems a load of armour stands are being teleported to some place on my world. I wish there was a way for me to find where they are all being teleported to.

 

not sure if this is a glitch/bug or me messing up a command block on accident, however, they only disappear when I enter the world before using any commands.

 

feedback and help would be amazing, thanks!

 

The same thing is happening with paintings and NPCs, they all just despawn after a while. Really annoying.