I had to troubleshoot a LOT of gear for a living, so figuring out ways to eliminate possibilities is bred into me now.
Actually, I'm glad it worked out for the best that it was nothing more than the dreaded Stax Fart haunting you. I was hoping it was that and nothing else, and the simple check of wiggling wires while it's off your head proved it.
Congrats on the relief of knowing there's nothing wrong with your cans! Nothing worse than that sick feeling in your gut that you spent some dough on something that has a problem.