First off, agreeing with the difficulty in communication/translation here.
One interpretation I haven't seen yet focuses on the splitters "going bad". I'd suggest a significantly-different potential at Comcast's ground point with reference to the rest of the system, causing current to flow through the devices and coax, damaging the bits inside the "splitter," whatever the OP may be applying that term to.
OP's "electrician" seems to be implying that there's 8V between "everything" and "ground," so I'm going with "OP's ground isn't very well grounded."
