Change log for 21.16 says, "Fixed issue with elevation calibration prompt appearing repeatedly"
Well thanks for that, I have NEVER seen this issue UNTIL my first outdoor ride after installing FW 21.16 yesterday and (you guessed it) I got the calibration message after loading the course BUT before pressing the Ride while I was viewing profile settings and then got another dozen or so more as and after I started the activity....so maybe NOT FIXED ? I have a location at my frequent start point with an elevation and also Auto Calibrate in the Altimeter settings, I will see if removing one of them changes the behaviour?