I had one go out on PA3X. You have to be very careful if you transport them in a soft case, because it sort of sticks up where it could be damaged if banged against something.
I don't think I did that though. I think it just broke.
Some people are replacing them with one from a Korg synth. Don't remember the details, but there is a thread about it on korgforums.com
DonM