Skipping Entity with id Warning

We started getting this warning spamming the console after installing MythicMobs. Don't know if this is a MythicMobs related warning or a coincidence and a different server issue. If MythicMobs issue, any ideas how to fix? Thanks.

[07.05 19:02:54] [Server] [WARN] Skipping Entity with id [07.05 19:02:54] [Server] [WARN] Skipping Entity with id [07.05 19:02:54] [Server] [WARN] Skipping Entity with id