I know not many people even use 77W anymore, but if you do, could you check channel 116 (SD only), and see if you are getting any video problems like this:
https://drive.google.com/open?id=0B0xcI6LxCtfUSWc3Q3NLc2JxV3c
https://drive.google.com/open?id=0B0xcI6LxCtfUSWc3Q3NLc2JxV3c