Launcher is outputting 'Skipping Entity with ID' errors massively

I have a Minecraft server/world file that is constantly generating the error 'Skipping Entity with ID'. No extra information is provided, it does this whenever a player is connected. I have tried killing all entities. The log file continually fills up all storage space on my server and I have to delete it. ~20gb of storage. Please help. Thanks

 

Video showing log output: Video

World File: World