This seems to be a major OnDemand bug (which Comcast will be slow to fix). If you can, try different ways of finding the program. Try going through the network listing to the network, then the program. Or try the alphabetical program list directly. Then try the search function. I've found all 3 can give different free vs. pay options for subscribed networks.
Hi Wrathfulfury -- I checked on this asset and it is setup correctly. The licensing for was not renewed by the content holder to keep this as a free episode. They have made it available for purchase only.
andyross -- This would not be an On Demand bug as the licensing to have this episode remain available for free was not renewed by the content holder. Please understand that the content holder can add/remove programming at their discretion or change the free vs purchase availability of their content. These changes would not reflect a major bug problem with our On Demand service. We do appreciate questions and feedback about content availability and we do work to resolve any confirmed issues with On Demand content.