Idk how but sometimes Bat mode bugs, I will not transform into bat or health will bug, (ITS ON SERVER)
Avoided by Creeper is not working on servers (Atleast for my server)

BTW This mod is awesome!!!!!!!!!!!!!

Happy that you like this mod :)
But I need a more detailed description of the problem and/or the log file of the server after the bug happened.
Also how good is your connection to the server? I've noticed some problems with bat mode with bad connections.

Closing since no response. Create a new issue with a more detailed descriptions if the issue persists.