In a common experience, an intermittent issue will frustrate someone for a long time, and then when s/he gets frustrated enough to spend the money and hire a professional, the symptoms of the issue will not be present. For example, a car makes a strange sound most of the time, but doesn't do it when the mechanic is around. Another example might be some intermittent medical symptom that disappears at the doctor's. The lack of ability to reliably reproduce the problem in front of an expert who might be able to fix it helps ensure that the problem will "survive" to another day.
Is there a word or few-word name for this concept?
I'm guessing that this is a phenomena perceived to be more common than it actually is.
It's almost the opposite of Murphy's Law because it's about something that can go wrong but doesn't, and it doesn't seem to fit the "simultaneous apparent opposites" that would categorize it as a "paradox" of any sort (e.g. it doesn't seem like mechanic's paradox would fit).