I just bought a pre-owned GPSr from Craigslist from a fellow cacher, and it seems to be great! except for one issue...I went to find a few (3) urban caches close to home to test it out, and all 3 of them were off by 30-50 feet! I found all 3 using geosenses, with a little help from the GPS, but once I was there, it was off! I even sat for a few minutes at each one to let it calm down, and the closest it got was 32 feet. This has happened before on my old GPS, but more like 15 - 20 feet. Is it a setting in my GPS i should change? It's a Magellan Sportrak Map. Thank you in advance for any help!!!