I'm curious of others have found a workaround for this:

Over the last month, whenever I try to book a F itinerary on UA via Chase Portal (using points as cash), whatever 2-leg F itinerary I find on UA.com (or any other site), will only be offered in the UR portal as 'mixed cabin' itinerary, with the first leg in F and the second in economy. The price is exactly the same as the full F itinerary on UA.com. I have seen this across several itineraries and date ranges. A phone call to Chase Travel did not resolve.

Has anyone else experienced this issue and/or found a workaround?