Recently i came across the bug coming in my server. I was trying to fix it but it was not helping. Then i went to their discord to ask for support they told me that i have outdated plugin. But in aternos its version 5.0.2 and the newest version is 5.2.0 but when i want to suggest it now it says can't beacuse its from Via external site. If there is a possible way to add the newest version can someone provide me with details how to add the newest version??
Waiting for response,
- Borpix 
Link for the newest version: https://www.spigotmc.org/resources/⚔-mythicmobs-free-version-►the-1-custom-mob-creator◄.5702/
