One day, almost 30 years ago, the manager of analog design at our start-up semiconductor company was having trouble with a design.
For those interested, it was an analog front-end for a T1 circuit.
It was behaving strangely, spitting out random bit errors, despite every trick in the book to clean up power and signal circuits.
One day, I walked into the lab to see how it was going, and he was at wits end... it ran all night with zero errors, but during the day it would spit out error bursts every few minutes! The light bulb went on.... I walked over to the Weller soldering iron, removed it from the holder and tapped it on the stand. Every time I tapped it, errors would occur.
He looked at me like I was some kind of magician, but it was just my years of debugging experience at play. By then, I was serving a sentence in Marketing, but I never gave up the chance to spend time in the lab.
Moral of the story: go find an experienced electrical person to help you out. Maybe he or she will spot the problem much faster than some random folks on the interweb. Be prepared to pay in $$ or beer.
Oh, that guy in the lab ended up as CTO of a $billion company.