I do sub in work for this band on an almost regular basis (couple few times a month). They had sac for a couple of years but switched to Behringer X32 rack a year or more ago.
This stopper actually has to do with the layout of the X32 app.
Originally they were using mute groups for the vocals, drums, ect. The problem was that they are all inears and they were used to sac where if foh was muted, they could still talk amongst themselves thru the mics and ears.
The foh mutes on the X32 mutes everything. The fix for this was to use dca's for the mutes.... Problem solved.
There are a few iPads around the stage so the performers can adjust their ears themselves. They use the Sends On Fader mode for this.
Tonight while the male vocalist wasn't singing, he went back to adjust his mix, and to choose your mix, the button you hit looks just like the mute group buttons (although they are located in a different place).
Well aparently they never undid the mute groups that they are not using anymore, and the vocalist muted the vocals, and then the instruments....
I didn't know what was going on and at first thought we had lost some power. As I am approaching the stage (I'm standing to the side of the dance floor with an iPad), I see all the vocals muted, ect....
The band freaked and just stopped.
I blame Behringer in part for letting a musician adjusting their monitor mix, to have access to foh controls like mute groups.....
I have also had on a couple of occasions where they didn't hit the sends on fader button and they were altering the main mix.