A/V Dropouts & pixelation with certain channels

Cable provider is Fios & I am using a Roamio. On certain (but not all) channels, I am receiving audio/video drop outs & pixelation. The signal strength for these channels is in the high 80's (last time I checked 87) so I don't know what the issue can be. Anyone have any ideas? Thanks.

A/V Dropouts & pixelation with certain channels