In that case he could temporarily replace the pot with two
resistors, right? And see if the circuit goes intermittent.

Because it always starts out working, and this is definitely
consistent. I really feel that this is an active component problem.

Maybe, maybe not. (I'm inclined to agree "yes, it is", when you say that the
transistor has the same voltage on all terminals.) But you really need to
put a 'scope on the unit, and step through it.