Epix Gen2 revisions ? Up menu button occasionally seems stuck and doesn't click

Hi. I have an epix 2 and on the package it says it is rev. A. Are there any newer revisions of this product available? I'm asking because the up-menu button has been acting strangely for a while now. That is, every now and then I get the feeling that it gets stuck (but registers changes in the menu) and I have to "unstick" it by pressing it repeatedly and then the click comes back.