Hi,
I am not too familar with the data diagnostic screens on the set top box menus, but there are a ton of things that can affect picture quality. Let me run down some things off the top of my head and list them: I assume that all of the sets are HD:
1.) How old is each set? A set's half-life is determined when the brightness level goes down to about 50% of when it was new. This does not mean that a set will stop working. Half life range begins about 9 to 11 years in or somewhere between 60000, to 1000,000 hours.
2.) Are you using an HDMI cable? How old is that cable? Have you tried a brand new fresh HDMI cable? This can make a difference?
3.) What stations are the worst picture-wise? Make a list. You mentioned pixilation or break up. That is almost always a signal problem and not a TV or a box problem. Are the stations bad all the time? Or does the station get worse during the day, or during the night?
4.) Where are you located? City? State? and Zip? Do you know neighbors with Spectrum TV services? If their reception is also bad, it has nothing to do with your set or hook up. It's a problem in your node. Get them to call in to report the issue! If six or more people call in to report the same issue, in the same area. Spectrum sends out an auto dispatcher team.
5.) Does a different model cable box produce the same results?
Provide answers to these questions and we can give further recommendations. We need your city, state, and zip, and makes and models of the cable boxes.
Satch