plugin crashes on use (paper 1.20.1)

[Rezztaq]

If i type /ec in chat or rightclick a physical enderchest, it does nothing but returns this in the console:
[23:32:18 ERROR]: Fatal error trying to convert EnderContainers v2.2.3-dev:fr/utarwyn/endercontainers/compatibility/ServerVersion.class
java.lang.IllegalArgumentException: Unsupported class file major version 25888

On 1.19.4 it worked but within the upgrade to version 1.20.1 it doesn't work anymore. But it works on a clean server without settings changed or any other plugins.

Plugin version 2.2.3 dev
setup is on a velocity proxy version 3.3.0 snapshot 307
server is paper 1.20.1 version 196
its a complex built network with server port 25574, redirected from the lobby 25571 by rightclicking an npc which runs '/server OGC-Factions' as the player

before it worked fine right until this minecraft version upgrade to the paper server. nothing got changed on settings or plugin list, it stopped working directly after the upgrade. Can someone try to understand/explain me the error? i didn't get the problem

just tried on a test server with the same paper .jar file and without the proxy in front of it. Just the new server and just the same endercontainers .jar file, it works too

[utarwyn]

Hello @Rezztaq! Sorry for the inconvenience.

The following error Unsupported class file major version 25888 explains that the version of java you are using is not supported by the plugin. But I'm surprised by the "25888" value mentioned in the error: this Java class version doesn't exist yet (Java 23 uses class version 67, for example).

Are you using a modified version of Java? Or a tool for manipulating Java classes?

[Rezztaq]

I created my own Modrinth modpack for server usage. I just know about that i can rename the text which is shown in the Window Frame (in Windowed/not Fullscreen)
but another server owner already told me that the server got problems to identify/understand my client version
If i start the same modpack (downloaded every mod from curseforge) in the original minecraft launcher and not modrinth, the Window text does not show the game version but "hidden by driver"

Its running with 196 mods/files (Minecraft is counting 306 mods in main menu) on Fabric Loader 0.15.2 in Minecraft Version 1.20.2.
Due to mod updates i needed to update the loader to 0.15.7 but the error persist

If i use the command, nothing happen. But in pure vanilla 1.20.2 (launched in original minecraft launcher and not modrinth), the chat throw an internal error message (which in my modpack does not appear)
Console:
[18:07:33 ERROR]: Fatal error trying to convert Endercontainers v2.2.3-dev:fr/utarwyn/endercontainers/compatibility/ServerVersion.class
java.lang.IllegalArgumentException: Unsupported class file major version 25888
--- and ---
[18:07:38 WARN]: [EnderContainers] Plugin Endercontainers v2.2.3-dev generated an exception while executing task 79864
java.lang.ClassFormatError: Incompatible magic value 1885430635 in class file fr/utarwyn/endercontainers/compatibility/ServerVersion