Seems like there's a crash occurring between Forgery 3.4.1 and Sinytra Connector Connector-1.0.0-beta.24+1.20.1.jar. Downgrading to the older 3.4.0 works fine.

Log: https://pastebin.com/4uiSLNYE

3.4.1 changed nothing todo with the crash...
so i guess, forgery release just broke somehow??
here unzip n try this it's the same version just re-compiled rebuild.zip

Otherwise please narrow down which mod is causing the conflict to something i can reasonably install.
since forgery 3.4.1 and connector-1.0.0-beta.24 standalone doesn't crash when i install them

The version you gave me seems to be working correctly, not encountering the issue so I'm not sure if it was just the compilation having an issue or if it's an anomalous error.

Anyhow if it's just a wierd compilation thing i'm just going to release the new version that adds a feature

you could temporarily use the released version again to find out

and super duper just in case add a crash handler for the inject that failed