So, to start off. I’m not sure if this is a bug with sponge, forge, or some other plugin I might have. Do know that this bug is occurring in other sponge/forge servers however (as I’ve been playing mostly pixelmon lately).
Bug I have noticed is that entities tend to multiply when they get ‘reloaded’. What I mean by this, is that when a player moves far enough away from a chunk so that that chunk isn’t currently loaded, and they come back, the entity gets spawned back in, like it should… but sometimes it leads to multiple npcs being loaded, npcs or item frames that were deleted in the past being brought back (and items duplicated), etc.
Found it odd that this bug wasn’t occurring in spawn, but then remembered that spawn is always loaded.
Also found out that by using a grief prevention plugin like grief prevention and disabling entity-spawn, it will delete all the entities in that area when returning to it. So, if I were to place an npc or a chicken, disable entity spawn, leave the area and return sometime in the future, the entities will no longer exist.
After realizing it wasn’t sponge, since just sponge didn’t cause the problems, I decided to test each plugin by itself (+sponge +nucleus because of commands).
For me, it was happening when I would close the client and log in again. At first I thought it was a client side version of the same sheep as well as a server side. Sometimes they would be stuck and wouldnt move. Then I realized I had four of the same named animal. But those also disappear sometimes and fix themselves. It was really odd.
What I ended up doing for testing was a sheep pen with a sheep of each color near where I was building. When I would walk by it I’d see i suddenly had 3 green and 3 orange, etc.
I updated this morning after I saw the entity related fix in the changelog. Tried to make it happen and so far so good.
I ran around my sheep pen, logged in and out, and I think I see the same amount of sheep. It’s one of those things that was hard to reproduce but you would notice over time. I’ll get you more details if it’s still going on.