I have had my Garmin Etrex Vista HCX for 2 years and it is still in top condition. You might just have had some overdrying happen due to heat. I don't keep mine anywhere where it will be in hot sun or a heat source. I',m careful that if I store it in the vehicle for long periods of time, it is kept inside the backpack at all times.
I don't know if this helps you or not.
Noisy Neighbours