I had the same problem..but it seems that it degrades over time. Also fast traveling in and out of areas seems to help. You can unlock fast travel stations by liberating the forts,although in my game so far i've liberated one fort and the new occupants seem just as eager to kill me as the Red Coats.
I think traveling on foot works fine also. It does not seem to go lower than lvl. 1 though. I have always a lvl. 1 in every frontier area.