protocollib does not support plugin reloaders

[itugra]

• This issue is not solved in a development build

To Reproduce
there is nothing wrong with what I did, I downloaded a ready-made package and I saw that I got this error. i thought it was because of a plugin, but no, I deleted all the plugins, I only have protocollib, but again the same error. i set up a server from the beginning, again the same error, I can't solve this problem, help me
!I DONT USE PLUGIN RELOADER

Screenshots

Version Info
last plugin version, last mc version

[Dymeth]

Version Info last plugin version, last mc version

The latest version of Purpur 1.21.1 is 2327, not
2284.
So what means "last plugin version"? Wich build number?

• This issue is not solved in a development build

Just try the latest development build.
Also problem may be solved in recently release v5.3.0, you can check the both.

If problem is still appears you need to provide full server startup log.

[blackysky]

I don't know, but could the problem be caused by remapped plugins from the .paper-remapped folder?
If I were you, I'd try deleting that folder and try again.