I had the problem yesterday on a BRU-LHR ticket I booked. I called up the Gold Line and they fixed it in about 5 minutes and charged the credit card for the EUR65 offer price on a EUR33 ticket (after EUR20 off with my Avios).

I forgot to mention that the agent told me that they have to book these in to U class - an non-Avios earning redemption class she said. So we have to phone and get it fixed after travel. I wonder if this has to do with the problems doing it online.