This is the first time this has happened for me, but I called in to Guest Services today to apply a Ritz club level upgrade certificate (from my Ritz JP Morgan card) for an existing reservation and I was told that the rate would be about $20 more per night if I wanted to use my certificate. The rate I had booked was the standard Member rate for their cheapest room and in the past they would just apply the certificate without rebooking at a different rate. I haven't used one of these certificates in a few months, so I'm wondering if this is one of the new Bonvoy improvements, or if the agent I talked to didn't know what he was doing.