For the first year of owning my 530, I had about 50-75 sensor drops per ride. So it sat in my closet while I continued using my 520. I finally got it to work properly last summer. Presumably the software eventually fixed the issue. I've had about a year of mostly trouble-free operation.
But, of course, it's a Garmin so that trouble-free operation wasn't to last very long. The cumulative ascent used to be reasonably accurate. Now, it's consistently 15-20% low. This is compared to friends' computers, my own 520, and the elevation correction from both Strava and Training Peaks.
I'll try running a hair dryer over the barometric pressure port in case there's any condensation, but that seems highly unlikely. I haven't ridden in the rain since February. Anyone have any ideas or fixes?