signal degradation

For about 2 months now the signal on DirecTV has degraded on some but not all channels. To the point where it is impossible to watch. We often get a msg to reduce resolution which helps only slightly. Last night's episode of Yellowstone was completely jaded with no understandable audio. It started with a slight twinge and steadily got worse. I switched to another movie channel which was the same. I switched a network station (CBS) and it was fine. 

We never had any problem for the 6+ years we had this until this fall. What can be done to fix it?