Originally Posted by
kallisthenis
I think it is worth trying a dummy booking of several tickets in parallel, in a different browser. Stop the dummy booking before the payment method and return to the original window and search for your ticket. (I think-) It worked for me once.
Yes I agree, this often works to force the booking into the next class. So - only if it's already in T and there are fewer than 9 seats left in T. If not, you could always just wait until S becomes available. The prices shouldn't change, unless there is a sale on that is about to finish. (well, obviously S will be more expensive than T but I mean S in a week should cost the same as S today).
In my experience, a Flex ticket in P is cheaper than waiting for S, but if it's already moved to U or T, then S will be cheaper than a Flex.