Running the newest current paper version for 1.21.4, I'm getting desync between the model and the hitbox, typically it doesn't re-sync and I just happen to find them via the particles.
Plugins:
AdvancedGUI, ArbitraryPortals, BetterStructures, BreweryX, ChunkLoader, CrucialAPI, EliteMobs, Essentials, EssentialsChat, EssentialsSpawn, Vault, WorldEdit, WorldGuard, FreeMinecraftModels, GSit, LuckPerms, Nascraft, packetevents, ProtocolLib, ResourcePackManager, ServerHider, Slimefun, TradeSystem
Does something here conflict with it that you know of?