OTA Issues.

I've had a Roamio Basic since January, and I'm very happy with it. Yesterday, I put a new Roamio Basic in for my parents connected to an outdoor antenna, and all was great for about 10 hours. All but 2 channels were pixelating very often. I checked the signal strength, and all channels are at 72 except 1 that was 62. I removed the small signal booster, and the pixelation was greatly reduced, but now the 3 weakest channels are in the 50's or lower, and of course don't come in at all.



What bothers me is that there is occasional pixelation on channels in the 70+ signal strength, and 2 of the channels never pixelate. Could there be some issue with the Roamio itself?



Any help would be appreciated.