Describe the bug
If somebody join before the "done", so when the server is loading, the server crashes.

To Reproduce
Steps to reproduce the behavior:

1. Start your server
2. Join before the "done"

Version Info
https://pastebin.com/TM2YKCfy

I'd take a guess it's plugin hider causing the issue.
You can permission /plugins so only ops or assigned staff can use it, if you're wanting to hide all plugins from your users (which is generally advisable)

Also, I believe you can set spigot.yml (I believe thats where the setting is), to hold player joins until the server is finished loading.

I'm not saying PL isn't at fault, but, if that works in the mean time, better than nothing :)

So, if I understand, the problem is not PL, but PluginHider.

And how can I edit that, because I checked for info in the bukkit.yml, but I found nothing. Any ideas ?

you would remove pluginhider.jar from your plugins folder?

BUt, you should try with the updated ProtocolLib first I guess.

Sorry, I forgot about this thread. The problem was actually with the plugin I used, not PL. Thanks for your help !