Wildman, I am not at all suprised by the random failures you are seeing after a "EMP" event. Todays electronics can fail, then "heal", only to fail again later.

I consider any electronics that have suffered such an event as unreliable and in need of replacement, especially if it is a life safety item.

I have attended many technical classes on static discharge and service work techniques that demonstrate the failure/heal cycle. Even improper touching of some components will cause changes to many components. Think about the problems in creating a static free workstation.

I strongly suggest that any equipment that suffered a failure and is now working be removed from service. Even competent repair technicians can not diagnose and prove safe equipment that has undergone a high static discharge event.