GPS cords are off

I have a Question for anyone that can fill me on what may be up. I have a garmin 76csx and up till now I only used it East of the Mississippi River. I started using it out West in Colorado, Utah and such places. Looking for Geocaches has been a nightmare because it's been off on every cache that I did find by about 200 ft. So I've been using my phone to get me closer than my hand held GPS. Am I missing something or what. Any though on this would be helpful. Thanks