Altitude Acclimation

The same thing is happening to me. I live at 5100ft, go to 10k a lot and my acclimation is decreasing.

Acclimation doesn't simply mean "going to high places".

If acclimatization is successfully completed, shouldn't the value drop towards zero ?

Based on prior experience, it's the other way around. It has normalized at the elevation you are predominantly at, so in this case, it should be around 8150' 

Ok, thanks 

Right, acclimation is adapting to higher places. My watch is struggling to record this adaptation. If I live and work out at 8000' I should become accustomed to that over time, and it not go down.

Can you pinpoint when it started...it seems to be tied to the V23 update 

Hm, from Garmin/Google:

"How does altitude acclimation work?
Example: If you spend 5 days at 3000m, you acclimatize to 2000m. Normally it would take up to 21 days of training at 2000m to reach the same level. The altitude adaptation will decrease within 21-28 days. The minimum acclimatization level is 800 m (2625 ft.)"

Is this supposed to be so ? I live in the lowlands, so no idea

I think the "level" referred to here is training level, not elevation level, it's basically saying if you train at altitude you get better faster

Also, some other folks reporting this too 

(+) Elevation acclimation - going down while at altitude - fēnix 7 series - Wearables - Garmin Forums

(+) Inaccurate Altitude Acclimation - fēnix 6 series - Wearables - Garmin Forums