Don't know if this system flaw has been reported but I ran into a very unique situation the other night.
I was trying to book an award flight from Sochi (AER) to LAX for Feb 2014 (return from the Olympics). When I input flights using the multiple destination page, it would show availability AER-IST-FRA-LAX. With the FRA-LAX flights on US Airways (stop / change of plane in PHL). However, it turned out that the PHL-LAX segment was actually phantom availability. Other routes also showed phantom availability. Could get all the way through inputting passenger name. I even called customer service and they said the PHL-LAX flight, in their system showed as cancelled. After trying various routes and combinations, was able to get the flights booked from IST-LHR-YUL-LAX. One leg was in coach so the system, as has been reported, did not price out the award correctly so I had to call and have the agent talk to the rate desk to get that straightened out (she did not want to call because she KNEW the system priced the flights right - but finally did and the rate desk got it corrected).
However, what was surprising was that when I went into my itineraries, it had about 8 or 10 different sets of flights on hold! It turned out that when I was trying to book a set of flights and the phantom availability showed up, it put the available flights on hold. So I wound up with about 4 or 5 IST-FRA reservations (2 people each) and about 3 or 4 IST-MUC flights on hold. As well as one FRA-PHL, one FRA-CLT and one AER-FRA flight. Some of the reservations were for C and some for coach.
Amazed that the web page would put all of these flights on hold for the same flight times (and in many cases the same flights). Also, when it put the tickets on hold, it took the seats out of inventory. That is why, whenever I would look for a new set of flights, the selection seemed worse until there were no available seats from IST to FRA or MUC.