I think I would start by asking Janty!
My LE stick was received with the same problem. The button just won't stay stuck at the corners. I sent an email to Janty last week and still have not received a reply. (cutting them a little slack since they were so busy shipping)
I'm not sure they have the replacement switches in stock yet but hope they get some soon.
Ludo suggested that you could just glue it down, but I'm a little reluctant to apply glue to my stick as it could make thinks a little sloppy, but I may have no choice if they can't replace it soon.