I can certainly relate to their problem. Those can be the worst sorts of problems to find - in particular, when you have an intermittent break inside of a wire. I've seen situations where a wire will ohm out correctly three or four times but still fails when you try to run the system. If the failure points directly to the wire or circuit as the issue, one can often deduce that this must be happening. The worst situations are when it causes a brief system-wide hiccup that is difficult to even catch. Those sorts of nightmares have been a significant aspect of my adult life.
For a good number of years, I was basically in the business of troubleshooting these sort of problems in large systems [ie. that was my bread and butter]
I once had a real oddball problem with a CMOS [maybe even TTL] Analog to digital converter in a new circuit I was designing for something... The chip would intermittently fail to output the proper value, but the voltage on the input pin was correct and a new chip didn't fix the problem; nor did a second new chip. It turned out that even though the voltage was currect, the current could actually drop slightly below the min acceptable value, which is unusual to see if the voltage on the pin is correct, and was due to a series of resistor errors that all happened to be high. That one had me pulling my hair out for days.