Huh, must have hit a wrong setting in the Pro page. Anyway, there is no Stop BGS command, just as there is no Stop BGM command. Rather, just play "None" through the normal Play BGS command.
Viewing post in How to Stop BGS?
Sorry for the holdup. I've sorted out the "fade BGS" issue, but I don't see a repro with game end > main title crashing the game. I'll try a few more things, but it could be caused by another plugin and it's just reporting that I'm the cause.
EDIT: Oh, ha. My fix to "Fade BGS" must have also fixed that; I undid it and reproduced the crash first try. Welp, two birds with one stone before you've even properly looked at the second bird I guess? I'll have that out soon.