Bad Hiking Distance tracking instinct 2s solar

Hi, i'm having an issue that i've discovered with tracking while hiking. 

I'm attaching photos to see the difference.

I'm am planning my courses using 2 apps + google research. (Locus maps and explore). I get a distance and I plan acordingly for it - equippment, food, water, even the people that i can call for this adventure. So when i get back and see that instead of 5 hours and 12.9 km, we did 15.57 and 6 and half hours (of course the hours will differ). 

As i've said, i am checking 2 maps + google research beforehand.

Dose anybody have a solution or suggetion for this?