Well cable management takes a few turns and twist's to reach it plug in point...maybe that twist and turns could make an lose connection on the power point itself(I may be wrong)
but what i have experienced ones is there was a lose connection on one of the power points like (The main power point that connects to the motherboard).
Maybe your motherboard has an bad connection somewhere on one of the power plugins on the mobo remember that the motherboard is connected to the casing and maybe thats where the shock comes from...(First the bad connection that makes the hole casing live throe the motherboards mountings) You get me?
But i may be wrong...Maybe get an tester to test electricity and test that area where the shock is and see if there are any live connection there...Its just an another thing you can try.