I am trying to use my Moto Razr HD to track my rides with Strava. The phone ends up cutting me across country and never gives me the same route on my circuit rides and cuts anywhere from .25 to two miles off the total compared to my bike computer. Is it normal for this to happen? The only issue that I can see with my use is I have the phone in a ziplock bag (to protect it from sweat) inside a cinch bag.

Does anyone else have issues with tracking rides with a phone?