I tried to remove all the names in "Mob Names" to just one name, and have it only use the whitelist otherwise. The config keeps refusing that when it's uploaded and just adding more lines with "use whitelist" and an invalid array.

Can you send one config file after you have modified it and one after you’ve loaded it once

I ended up fixing it by editing the client one and overriding the upload via FTP, so it's likely the bug is not on your end and something else funky is going on.