Interesting ... agree it seems to be pointing to breadboard or wiring or something similar.
How many miles on that breadboard? I'm pretty surprised that I don't have more breadboard issues than I do, they're really quite rare, but most of mine are relatively new.
Mine are all ropey as hell and half the tracks don't grip any more - those that aren't melted from overheating components 
Haha I've used this breadboard quite a bit, and there are even some spots where the plastic is a bit melted. I think it's time to retire it.