Multiverse-Core: Can't change settings.

I'm currently running Multiverse-Core on my server. I have multiple worlds including one for my creative plot world. Whenever I try to edit anything in the config it always returns to what it was before. I want to turn off spawning of mobs in certain worlds, and I'm not able to do that because it always reverts back.

Is there anyway I can resolve this issue? If you need any information about plugins, logs, and etc just let me know.
- Thanks,
Zerekify

 

Yes I've tried restarting & stopping the server after editing but I will try another method.

 

I will try that, and has this worked for you?

 

Thank you so much. I have done what you said, and it is working!