The evening of 2/20/19 I saw that there was a 12.5 update for my 935, and I applied it. Things seemed fine, but then I started seeing bad elevation data on runs/rides. Not like the 32,000 feet of elevation I've gotten before, when the Barometer has died, but a major change. 2/20 was also the last day my stairs climbed shows any data in Garmin Connect. My same short 5k route I run weekly shows this (the oldest 3 dates I'll concede temperature swings, but the hills didn't get 4 or 5 times higher):
3/12/2019 - 410
2/21/2019 - 561
2/19/2019 - 95
2/7/2019 - 82
2/5/2019 - 69
Anybody else seeing this? I've done the soft reset already.
