After I called Comcast they sent a tech to my veranda.He checked the signal coming into the building and it was strong then checked the signal coming into my den ,which feeds all my TV's and that signal was weak,indicating a problem between the end ofthe building and my den.Then he checked & replaced every spliter he could find, then put a booster on the line coming in my den,PROBLEM SOLVED.
The tech was fantastic.
Maybe this will help you guys.--------------Good Luck ------Jack Tyndall