We went in 2013. I booked online, no issue with availability. Tickets had to be picked up from the machine at Lawson.
However I couldn't get it to work at the store because I couldn't find a way to enter my name in English, to match with the online booking. So I had to start the process from scratch there, using that machine and typing katakana for my name.
Also because of that I know ticket availability online is same as in-store. Now the machine supports English input for names.