Just recently got my Instinct. Coming off from Fenix 3, its great to have lighter watch, and a more appropriate watch face size on my wrist.
Did my first run just this late afternoon. After my phone has sync-ed, was surprised to see the Garmin Connect dashboard show I climbed 58 floors up and 60 down. I went to check on the activity, on a generally flat pavement run, this was my recorded elevation profile as shown on Strava.
I traced through the route, those drops are on road crossings where I had to wait for the light to turn. Looks like it depends on how I was waiting, likely when my arms on my hips, the closer the watch is to the wrist, then the more likely the folds of my skin gets pushed to cover the hole for the barometer.
I went through the forum, turns out this elevation issue is already a problem. Though from my experience, its way too easy to trigger with the results way uglier. Not willing too buy the 3D printed parts, too expensive when shipped to my part of the world.
I hardly experience this on my Fenix 3, likely due to the design with the port further away from the skin. Maybe I should have waited for the 2nd gen Instinct, they must have fixed this in the design.
Or maybe I can try wearing it on my right wrist. Hmm.