Hello,
Well, what I found is that vertical and horizontal transponders sometimes have different signal qualities. And, some of the radio channels have a much higher signal quality than the video.
At my location I have not seen what you have experienced. If all of your equipment has not changed, and you still are receiving signal, I would say you may have had some shift in your dish position. This can be due to high winds or someone bumping against the
installation. Did you have that recently?
Also, rain and heavy fog could cause a temporary degradation in signal quality.
Check to see that all your coax connections are tight and clean. If that is the case, I'd go out there and do some adjustment to the dish to re-peak the signal.
Hope this helps.
Spongella