How do I fix the calibration for my Vivoactive 4s and treadmill?

How do I disabled GPS in treadmill-mode (started activity)? I thought "treadmill"-mode automatically disabled the GPS. 

Most of the steps is counted. But sometimes stepcounting stop registration. Fast walking 140-150 steps/min.

In example 40min walk, 5950 steps, 0,33km (in VA4s), treadmill shows about 5,6km.

I am not sure how to deactivate GPS in treadmill mode. I agree it should be automatically deactivated. I have noticed that a friend of mine has automatic activities, and he gets maps from his walks outdoors, which indicates that the watch switches on GPS automatically when he starts walking. Maybe this can happen even when you have manually started an activity?

I also missed doing this on my first run. Then when I attempted to do it again (running 2 miles) the watch said you must do between 1 mile and 1.43 miles so I did 1 mile for 3 days straight hoping to see the option to calibrate but the only options shown are discard or save. No longer showing me an option to calibrate. Any help would be appreciated.

On the Vivoactive4 you can swipe up from the save screen after your activity and it will give you the option to calibrate after every treadmill activity over 1 mile (recorded by the watch, which we all know is way off).

I have been saving and calibrating my watch after every single activity, it is getting closer to being more accurate, but it is still off every time! The other day I ran 1.5 miles on the treadmill and it said I ran 2.25 miles. But two days before that I ran 1.5 miles on the treadmill (Same speed and incline and everthing) and it said I had went .97mile. I honestly do not understand.

What I would like to see is Garmin overestimating the distance, then we could hone it in. So, say we walk 1 mile, Garmin is generous and says we walk 1.25 mile. Then we could dial it down to a more accurate number. But like you said, it is always lacking where distance is concerned and I would have to walk 2 miles before it would register a single mile. 

Try doing some outdoor running/jogging activities with GPS. That will help with the calibration. I think Garmin is afraid of overestimating distances, because some people would use it to cheat in distance competitions.