This has been fixed. There was a quite huge area where all elevations were at zero. It was a bug in our external source service for elevation data. We reported it, and they fixed it within two days.
Our affected data has been updated accordingly. Mentioned Geocache is now at 3874 meters.
Everything with this was potentially affected:
latitude between 37.9 and 42.1 and longitude between 43.9 and 50.1