I had a fun one...tried booking FRA-INN-VIE-CDG on 016 stock, all on OS. The last 2 legs ticketed immediately, but the first leg (FRA-INN) refused to ticket at all. I called 1K line, and they said that OS would not ticket the first leg. I had to have all the flights together to get the pricing (~$230), otherwise the prices got quite expensive. In the end, I just booked everything via OS' website, as using miles would have not been the best redemption rate.
Perhaps part of the issue was that FRA-INN and INN-CDG (via VIE) were 11 days apart, and that caused some kind of issue?...