I don't think signal loss is the issue. You're not experiencing the pixelization (dissolving picture followed by acquiring satellite signal error) associated with signal loss. I know you say you have checked the HD setting, but if you would check it again. Dish remote - menu - system setup - HD setup - make sure it is set on 1080.
Then try going into your TV settings and try adjusting some things. The are various picture settings (vivid, movie, game, etc) as well as blackness, sharpness and other settings that may restore it back to how you want it.
Other than that, I'm out of ideas.
Then try going into your TV settings and try adjusting some things. The are various picture settings (vivid, movie, game, etc) as well as blackness, sharpness and other settings that may restore it back to how you want it.
Other than that, I'm out of ideas.