Vent bypass does not stay on

What is your question?

I depress the little car icon so it is lit and only cabin air is circulated while running my air-condition. However while driving down the highway, I notice the car icon is no longer lit and I am venting outside air. Why does this switch to outside air ocur?

What makes this problem better or worse?

Does not apply

How long has your 2018 Kia Sorento had this problem?

I just noticed it