Ah, sorry, missed this one! Will prioritize it

I'm not quite sure why this happens uniquely to you. That's a GUI error, which pretty much everyone should be getting, including me :(

Any errors/crashlog? How does it crash? Does Unity/Shader Forge crash or did the shader just not compile?

(After closing Unity, then reopen it)

Try deleting Library/ and Temp/ folders in your project folder first too, to clear the cache

That really shouldn't be possible at all, there's nothing that writes gl_ anymore. It sounds like you may have shaders using the same path (a result of duplication), where you've only recompiled one of them. It could also be a cache issue, or a selective recompilation issue, where Unity doesn't recompile the GLSL path because you're not currently using it.

This was fixed in 1.21, do you get it in 1.21 too, even after recompiling?

Does it happen in a brand new shader too, or only in the old ones?

I can't reproduce it on my end :(

This is now fixed in 1.21