Hello!
My new Fenix 5x+ does a very strange thing. My altimeter is set to "Auto" and I have manually calibrated it to 207m. When I start moving around the house, the watches may start counting floors -- I have 3 today already, even though I was at home all the time. The atmospheric pressure is decreasing today, but I think I've seen this even when it wasn't doing that. While decreasing pressure might explain why the floors are being counted, what's puzzling is that the altimeter still shows 207m. I.e., the watch says that I'm staying at the same altitude, however, it's counting floors!
I would understand if the height would also increase (due to decreasing pressure while I was moving -- easy to assume I'm really moving upwards), but no, it's still 207m for more than several days. Any clues?