GPS not working since day 2

Hello Everyone, So, I was able to finally find an SX Prestige (not the color that I want) but, unfortunately, I notice after the first day that the GPS was getting off, after the second day, the GPS was off for almost a mile, I took it back to the dealer and it took them 3 weeks to replace the whole unit. I picked up the car, and then again after the first day... now they are going to see if the antenna (also replaced with the whole unit) is the problem.
Did any of you have a similar problem?
Thanks!