PS for Andrew -- here's one typical source on how semiconductors can be "wounded" and experience intermittent failures. We usually don't notice intermittents or understand there's a problem until a catastrophic failure develops.
https://www.allaboutcircuits.com/textbo ... discharge/
This is one reason so many uninformed young repair techs claim they've never needed to use ESD protection and never seen a problem from that lack of precautions.... two types of failure modes: catastrophic and latent. Catastrophic is the easy one, leaving the part completely nonfunctional. The other can be much more serious. Latent damage may allow the problem component to work for hours, days or even months after the initial damage before catastrophic failure. Many times these parts are referred to as “walking wounded” since they are working but bad....
https://www.allaboutcircuits.com/textbo ... discharge/