Ex Maintenance anything left behind or a dimmer low setting?
I believe that the A/C had only recently had a hangar visit.
Could a spanner have been left in a sensitive location? It has recently happened to an A380 after delivery. A little rocking and rolling during CB avoidance could allow this excellent conductor to come in contact with a high current Bus bar.
The other problem in the past with unintentionally entering CBs was the WX radar display dimmer left in the minimum position. Highly unlikely that both could be left in the same position. Some airlines ask that the PFD and ND CRT displays be reduced to min to extend their serviceability. But unfortunately some crews turn both the ND and WX dimmers to the minimum position. The WX, as per SOPs, is off so there is no need to turn the WX dimmer down.
The next crew may be unaware as all would appear normal unless there was lightning seen to alert then to look ahead on the WX and realize that the dimmer was turned right down.