Inaccurate location results normal for a Garmin

My new Garmin Nuvi 755T instructs me to turn, after the turn was already made and I am about 100feet up the road. At some intersections,while i am waiting for traffic so I can turn, it shows that I already turned and it instruct me to go straight. Garmin stated what their wide range of acceptable inaccuracies are, but I don't buy the excuse. My girlfriends $100 Magellan is right on the mark as well as my Delorme $49 PN40. So why is the performance of my $400 Garmin so poor and Tech support stated a reset is all I can do(which didn't work)