Cable is pixelated

Cable tv is pixelated and picture/sound drops. I also have Xfinity cable. Newer Nighthawk modem.

Cable tv is pixelated. Netflix/Hulu, DVR are clear pics.

I tested coax port from wall. Good.

New coax cable to modem

New splitter.

New coax to box.

New hdmi to box.

New DOCSIS filter on coax to box.

Picture pixelated after each change out and test. 

I am out of ideas.

I want a tech to come out and check the lines and he told me had to come inside first and cannot just check the outside. Though when I booked the appt, the CS never said that was a rule. I have a disabled parent and pets in the house.

Any suggestions on remedies?