I have a Oregon 400t of Taiwan version, The latest software of Taiwan GARMIN is v2.80
I encountered about the GPS accuracy problem two times, you can see the problem from the following picture.
I stay here over 10 minutes ... Oregon 400t keep error ...
Oregon 400t coords : N23 12.296 E120 39.992 (Over 100 meters)
60CSx coords : N23 12.235 E120 40.035 (correct)
Oregon 400t GPS Elevation : -77m (Over 500 meters)
60CSx GPS Elevation : 479m (correct)