What is electrical transient?
"Electrical transients are momentary bursts of energy induced upon power, data, or communication lines. They are characterized by extremely high voltages that drive tremendous amounts of current into an electrical circuit for a few millionths, up to a few thousandths, of a second."
https://alltecglobal.com/articles/wh...cal-transient/
If some part of computer logic has been switched by a voltage spike during a "transient" (not simply changing a power supply source), then sometimes it takes more than a simple 10 second reset. I don't understand why shutting the engines down and attempt another reset whilst on ground power or APU power would make a difference - but if you are still on the ground - then that option is still available.