I'm not sure if it's related to Java version, but since it's the first time I'm seeing this and I've made some changes recently, it's my primary suspicion.

I'm running official oracle GraalVM Java 21 released a few days ago, with 1.19.2.

Using these flags (I now use ZGC, but these caused the crashes):
-XX:+EnableJVMCI -XX:+UseJVMCICompiler -XX:+EagerJVMCI -Djvmci.Compiler=graal -Dfml.readTimeout=120 -Dgraal.ShowConfiguration=info -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -Dsun.rmi.dgc.server.gcInterval=900000 -XX:+DisableExplicitGC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=51 -XX:G1HeapRegionSize=32M

I get occasional crashes about different stuff. One was this, as soon I made a world and was waiting to get in:

java.lang.SecurityException: SHA-256 digest error for net/fabricmc/fabric/api/event/server/ServerStartCallback.class

The second time it was this

java.lang.SecurityException: SHA-256 digest error for net/fabricmc/fabric/api/block/BlockAttackInteractionAware.class

Java 21 should work fine, what operating system are you using? I vageully recall seeing this issue before, I forget what the cause was though.

Windows 10. Never had a similar problem up to this point.

I assume you have tried redownloading FabricAPI? This could possibly be caused by a corrupted jar file.

The jar itself in mod folder? The crc seems to be fine...

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