On my older Magellan Color Trak there is a screen display of satellites the unit, GPSr, is tracking and the azimuth (direction / bearing) they are from the GPSr and their relative signal strength/quality. These will vary during the hour. This variance will cause your GPSr to show varying 'best estimate locations' Anything more than ddd. mm. ss. 3 (.3 of a second) is the unit using "Kentucky windage".
A ddd.mm.mmm' display would only be accurate to .005' plus or minus 95% of time
I believe that sat locations at given time is the key to accuracy. Weather,clouds,rain or shine have little affect on the GPS lat long reading. Sunspots are another subject.
I suspect that comments regards the cache being misplaced could easily just be that maybe the GPSr reading was recorded or viewed by each user at times when distortion was the greatest. Many a time at sea, the GPSr fix would be off the plotted course significantly; a look at the satellites being tracked would show poor triangulation or maybe only 2 satellites active, usable above horizon, at that time, wait 20 minutes and the GPS position would come back in line.