Garmin GSC 10 speed sensor issue
Been having some issues with my Garmin GSC 10 speed sensor. I run it with an edge 800, and the speed sensor / cadence are only on my indoor training bike that I ride on the rollers, so it's never been outside. Have had it 7 months and just started having problems with it.
A few days ago the speed sensor starting acting very strange. Did 45 min on the rollers and the speed sensor wasn't working; total ride distance was 7 ft. Heart rate and cadence seem to be working fine.
So I changed the single battery on the GSC 10 and did another ride. Speed was now showing up, but was very sporadic; showing a lower than usual speed, sometimes seemed accurate, and then when I really starting hammering, getting up past 20mph the speed would jump from 20 to 10 to 0 to 20, etc.
I've since checked and double checked the magnet position/alignment, recalibrate using the little button on the side of the sensor, and cleared the memory on my Garmin. Rode again since doing this and the speed sensor is still not working right: sporadic readings (sometimes showing 1/2 of what the speed should be), 0 mph for a few seconds when I really put the hammer down, and just seems low from what I am accustomed to seeing on it while riding the rollers.
Any troubleshooting suggestions or tips? What else should I try? Thinking maybe the speed sensor went bad and I should just warranty it?