I would suspect a little dirt, that is making it stuck (for a while) in one position... Before taking it to repair shop, I would disassemble device and check it myself - it's as easy as unscrewing 6 screws, really.

Either "faerie" is visible, or (if you check pressing that button on MB yourself, and it seems to work OK), it's really damaged switch. In the latter case, repair center sounds sane - one could attempt to replace that switch her/himself, but it's not trivial for beginners (small parts, SMD).

/Estel