Have noticed completely bizarre availabilities with EK on a number of occasions as well, including the example mentioned (availability of a loser booking class while the higher ones are 0). It is not just an EK website issue, but you will get the corresponding availability also on tools along the lines of expertflyer. I put it down to IT glitches (programming or perhaps update cycles), since I haven't come across this yet with the other carriers I fly, but maybe that is just a coincidence. Anyway, perhaps someone has some inside info and can comment.