Shows not playable, except via another Tivo (!?)

I have a rather bizarre issue that I have never seen in 15 years of owning a Tivo. I have a folder of 35 recordings of Shark Tank, all taken from the same CNBC HD channel. Of these 35, only 4 can be played properly. The rest give me the following error:

Error playing a recording - The Tivo box was not able to record this program because there was no video signal on the channel. You may have been trying to record on a channel that you don't receive.

The thing is, not only do I know these shows were playable until recently, I can still play them now FROM ANOTHER TIVO. No error, no problem, using Tivo-to-Tivo streaming.

Both Tivos are Premiere XL4 at the current software level. I called Tivo and they were stumped. I don't expect any more help from them, especially since I have a workaround. Still, I was just wondering if anyone else had seen this behavior. I would say it was a disk error except for the fact that the shows are playable through streaming. Maybe the process of reading the disk locally is different from reading it and streaming?????

Like I said, I can live with this problem as long as it doesn't spread to other shows...but I'm still curious.

Thanks in advance,

Rob from AZ