TLDR: don't press the creation code button on the room that you want to live edit.

When setting up a live room, clicking on the creation code button of a room borks the server.

I had to create an entirely new room to fix the issue. 

That is fixed by adding anything (e.g. a comment) into the room creation code - the deal is that GM will "link" the RCC in the room file when you click the button, it removes the RCC file if it's empty, but it does not unlink the file from the room file, so to GMLive it looks like your project is missing files (well, it's impossible to tell in this case). I'll make this not error in the next release.

This should be fixed in 1.0.22