I had a similar issue with the Nav (actually many times at different locations), but in route to the Independence, MO supercharger from St. Charles, with about 100 miles to go, I entered the Independence supercharger as my destination. The Nav told me to turn around head back to St. Charles, into IL, WI, MN, SD, and down through IA to get to Independence. This was a 1200 mile detour. I was about 100 miles from Independence with plenty of charge left (10% extra) at the time I entered the info in NAV. No idea what logic was used to guide me.
No, I didn't turn around.
I just finished a solo cross country trip, and many times the NAV would send me back to a supercharger right after I had done a charge with +15-20% above what I needed.