Uncaught exception in thread "main"
java.lang.RuntimeException: Failed to read accessWidener file from mod nbteditor
    at net.fabricmc.loader.impl.FabricLoaderImpl.loadAccessWideners(FabricLoaderImpl.java:529)
    at net.fabricmc.loader.impl.launch.knot.Knot.init(Knot.java:149)
    at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:68)
    at net.fabricmc.loader.impl.launch.knot.KnotClient.main(KnotClient.java:23)
Caused by: net.fabricmc.loader.impl.lib.accesswidener.AccessWidenerFormatException: line 1: Namespace (named) does not match current runtime namespace (intermediary)
    at net.fabricmc.loader.impl.lib.accesswidener.AccessWidenerReader.error(AccessWidenerReader.java:285)
    at net.fabricmc.loader.impl.lib.accesswidener.AccessWidenerReader.read(AccessWidenerReader.java:84)
    at net.fabricmc.loader.impl.FabricLoaderImpl.loadAccessWideners(FabricLoaderImpl.java:527)
    ... 3 more

Minecraft: 1.21.1
Mod: 2.0.2.999

my gf crashed like this too but this fixes itself randomly

Are you using a custom client or something? The error itself is bizarre, but on top of that the fact that it fixes itself randomly is even more bizarre
Also make sure that you're using the .jar from the Artifacts.zip/libs/ folder, not Artifacts.zip/devlibs/

same issue, even with a clean launch with zero mods except that and fapi, dev build tho

Yes I am using that jar
And I was using Boze but again it fixes itself randomly. On top of that, my gf gets this error though she doesn't use boze just fabric

Looking at the code, this seems basically impossible, unless this is a 1.21.1 thing (highly unlikely) - since I haven't started 1.21.1 support yet, I'm not even setup to look at 1.21.1's code yet
Can you either upload the .jar file you're using or check the .accesswidener file? To check the file, rename the .jar to .zip, then open the file nbteditor.accesswidener with Notepad - post if it says accessWidener v1 intermediary or accessWidener v1 named at the top of the file.
Presumably you're 100% sure that "fixing itself randomly" isn't actually just you downloaded the next dev build and happened to grab the correct .jar that time?

well i am on 1.21.1
and no, i haven't changed jars at all I've only downloaded the next build once
also it says accessWidener v1 intermediary