Obviously, the recommended approach is to return it to Eventide, especially if it is still under warranty..
Otherwise, the problem will be one of the following:
1) A broken switch. Hard to fix. Contact firstname.lastname@example.org and plead for a replacement.
2) Some dirt in the switch. Cleaning may help.
3) Bad soldering of the switch. Fixable.
4) A mechanical issue – may be fixable.