Server Overloaded

*I don't speak english as my first language, but I try my best.

I run a vanilla server on the latest Minecraft version with 4 slots for more than 2 years. But it doesn' really run any more. The Server is overloaded. If I looked for the log file, the Server says: "
[17:17:53] [Server thread/WARN]: Wrong location! wd['Bat'/405, l='world', x=18.55, y=54.10, z=150.78] (at 1, 9 instead of 6, 12)" You get the Log file as an attachment.

Now, I'm not able to play minecraft. what I tried to do is turnig off the hostile mobs, but there still is a bat, i have a problem with; I could turn off animals, but I don't want to do this, because that would awful for me and my friends.