TL:DR - I do not expect it is your setup - rather something to do with Comcast's underlying service.
I have the same setup - Tivo and Xfinity - in the North East of the US. And I have the same problem. It shows up for me on CNN. I don't have splitters, just connectors, in the path from the service to the Tivo - and only two of those. The signal strength is 99% and dB value is reported at 39 for the channel that freezes and drops out. It started for me 3 or 4 days ago.
I have heard that Comcast is rolling out changes to it's internet service. I don't know if that might have some interaction with the cable service. If some part of the path from the source to the local cable is delivered over the company's internet backbone perhaps it does.
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