137-140 are the ‘family area’ so you have to have a certain ratio of adult to child tickets to book in there.It's weird indeed. Maybe if you don't use the map to select specific seats it's been allocating South to North in direct contradiction of the comms. Would also explain why blocks 137-140 have loads left while their mirror image seats in the other corner almost sold out.
Does anyone know if the website actually stops you buying tickets without the right ratio or does it just give the restrictions warning to try to dissuade the purchase?