A mod is patching code that does not exist here
Applies to Forge, NeoForge, Fabric, Quilt.
What causes it
A mod tried to inject into game code that is not present in this Minecraft version, which almost always means the mod build does not match the server version.
How to fix it
The trace names the mod behind the failed injection. Install the build of it made for this exact Minecraft and loader version, or remove it.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log