The venerable Wessex had electric fuel computers which would freeze the throttle actuator in the event of loss of signals (NF, N1 etc) but also if the battery voltage dropped below 18V if memory serves.
The problem was that once frozen, you could only recover the engine from it's frozen power level by bringing it back to idle.
Due to a series of electrical problems and a lack of a voltmeter, it was possible for a bad generator to drag the good one off line as well and result in rapidly falling battery voltage.
This led to a number of double computer freezes in tricky conditions.
We used to pull to just under max twin Tq on the first transition of the day and at that point, with a moderately low cloudbase, a colleague discovered that both had frozen and he was zooming skywards.
Fortunately he managed to get one back to idle and avoided IIMC but was till left with the other stuck at a high power setting.