Some channels won't appear on some tuners intermittently

I have a 6 tuner Roamio and three Minis connected via MoCA. The past week or so I have been experiencing an intermittent problem where it appears that some channels will not display on some tuners. The first time this happened, I tuned to our local CBS affiliate (705 Comcast HD) from the Roamio and I just got a black screen. Other channels would come in fine. I went to one of the Minis, which is served by the same Roamio, and was able to tune to 705 fine. After which, I was able to get to the same channel from the Roamio. This morning, I was trying to watch NBC HD (703) from a mini and got an error about trying to connect to the tuner. Going to another channel worked and all channels seem to be working from the Roamio.

So, my cable signal and card seem to be working properly. I am wondering if I have a bad/failing onboard tuner? But, that doesn't make sense as from the same Mini I can get to other channels, and presumably the Mini uses the same tuner on the Roamio?

Any ideas?