Elevation incorrect / Barometer broken?

Since two weeks or so, my elevation on the EDGE 830 is way off.

Does anyone have an idea what the cause could be?

https://connect.garmin.com/modern/activity/6952608886 (During this activity I scaled Großglockner Hochalpenstraße, which was at 2.500 meters, the EDGE only put me around 1.000 meters..)

This is really annoying.

I can provide more examples if anyone has an idea and more data is required.

Appreciate any input from the community.