There is no option to calibrate the treadmill after I complete a run; the option seems to be missing.
I posted this same issue a little over 3 months and got no response as well. Looks like they don't care or it was removed.
I remember reading something like to delete some files in your watch.
I have not tried it yet though.
This is to trick Garmin that you have not calibrated the watch.
You can explore and try moving those files.
Same problem for me. No “calibrate and save” option after running in Treadmill mode. Epix 2 with up to date firmware.