Cable Card HD channels disappearing - XFinity

I have a Sony TV which uses a cable card. No TIVO or DVR just a cable card. In the last few months I have lost video on over 25 HD channels but not all HD channels. I can receive audio but no video. I can receive audio & video on the SD channels. I have talked to support 3 times and a tech came out. Tech had no idea why and suggested a new card or going to a box. Why am I losing some but not all HD channels?

This question, "Cable Card HD channels disappearing," is about XFinity-Comcast TV channels, programming, and sports.

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