This includes routine maintenance. It s no longer acceptable to pop an old part out and plug in a new one any ole time. Those days are long gone. Disruptive maintenance practices must be done during hours least likely to affect subscribers say, midnight to six and should be scheduled well in advance. Part of this scheduling includes notifying the subscribers that will be affected so that there are no surprises.
Sloppy workmanship is another source of intermittents.
You re no doubt familiar with the flashing picture syndrome. A little detective work usually turns up a loose connection somewhere. Someone forgot to tighten the F fitting at the tap. It s not a pretty sight. I alluded to a third category of sorts.