I think there could be many threads about what went wrong at a gig. Just when the band is ready and you are about to bring it, it turns out something small has happened in a big way.
Oh, but I bet your rig with those two Bergantino HD 210 cabinets is a monster!! I'll need to check out the TC Blacksmith bass head, too!
So, back to gig pressure situations. I'm primarily a church musician and I don't leave my gear, so I have to set things up and tear them done. One Sunday I'm running late and taking this new Demeter bass amp I had just received that Saturday, which doesn't have Tuner Output. In a hurry to get set up, I unknowingly plug my guitar cable into the OUT on Seiko Tuner and plugged the IN on the Tuner into the amp.

Everything powers up but no sound. I'm like, 'WHAT!?!'. I'm checking everything, and of course the Tuner looked like is was fine. So, I'm thinking something is wrong with the amp. The MOM (Minister Of Music) is asking me if I'm ready cause the service music needs to start and I checking all the cable connections, and switching things around to the cabinet, and even checking the battery in the bass. Of course, they start without me, and I'm beginning to sweat a little cause this is so simple and I've done this so many times before.
So, as the first song was well on its way without me, I sit down in my chair thinking 'I'll just sit this service out!'. Then a still small voice said, 'Look at the Tuner!'. And with that glance it was so obvious as to how wrong I had run my cable into and from the Tuner!

I was like, 'I just know some musician(s) in the congregation watching me go through this and laughing!'.
It was a 'DUH' moment, for sure!!