I've been dealing with this nonsense for months. They sent me a new STB that didn't fix anything, I've replaced the coax and reset my STB more times than I can count.
I'm so sick of being over charged (yes, Verizon's billing is lousy but that's another thread) for services they are NOT providing.
When the contract is up I'm switching to something else, Verizon is awful.
When you say replace the coax do you mean the part that connects to the wall plate? Pixelating channels could also be your ONT, splitters, or wiring. It sounds like you might need a technician visit.
Start a new topic or ask questions in the open forum.
