For an issue like this, if it is a High Definition TiVo of any kind there are some diagnostics you can check to see if the issue is signal related.
1. From TiVo Central, select Messages & Settings > Settings > Channels > Signal Strength - Cable.
2. Press SELECT to display the Signal Strength Meter. A Warning screen appears, telling you that using the Signal Strength Meter will stop all recordings.
3. Highlight OK, access this setting and press SELECT. The signals strength meter appears.
Then we need to check the signal quality.
1. Tune to a channel that is having a problem.
2. Write down the channel number and then press RECORD to lock the tuner to the channel. (If two CableCARDs are installed, this also locks the tuner to the CableCARD.)
3. Press the TIVO button and select Messages & Settings > Account & System Information > box Diagnostics