From some of my experiences, I have seen some similar occurrences.
One was in a Victorian house were the wiring was a bit obsolete, the other was in a village were the electricity supply tended to fluctuate.
Have you got surge protectors for the machines, as I wonder if you have had a spike of electricity. Repairing the above machines and installing surge protectors, resulted in no further problems. That and instilling the need to disconnect everything when thunderstorms were present.
I just wonder if the problem has been with an electricity spike, just a thought