TiVo Roamio unable to buffer/record one specific channel
I bought a Roamio a week or two ago to replace a Premier box. I have Comcast cable in the Seattle area.
In my Roamio, I'm unable to record or buffer at all on channel 113 (my local FOX affiliate). If I watch it for several minutes (the picture comes in just fine!) I still cannot press the instant replay button (I get the TiVo Boing sound). If I pause it for a few minutes and press play, it instantly catches me back up to live. The green bar does not fill up.
If I attempt to record on this channel, watching while recording causes it to display a black screen with something along the lines of "Recording program, press Play in a few seconds to begin."
The cable card signal and snr on this channel are fine (at least as good as others). I've tried rebooting, redoing guided setup, putting all tuners on this channel, putting only one tuner on this channel. Nothing seems to have any effect at all.
I called TiVo, they said they'd never seen this problem before, had me walk through my cable card diagnostic menus, couldn't find a problem, and then told me to get a new cable card. Comcast doesn't want to give me a new cable card (at least without wasting my time by sending out a technician), and tells me it's my Tivo boxes fault.
Should I call TiVo and insist on a replacement? Something's clearly wrong here.