I turned off auto pause and it stays off.  I press the stop button if I need to pause.

Keep in mind also that you can set the recording frequency. Depending upon the gps, it could be as short as every second or two, could be a distance (50ft), or could be "smart recording" or something like that. Smart recording tries to minimize the recordings needed and still accurately cover the route. On flat, straight trail, it might record every 10-20 sec but maybe 5sec on twistier trails. When I'm gps'ing a trail for some application (like our local trail maps), I'll try to remember to set my recording frequency to 1 sec AND keep moving along the trail (not wandering off through the brush) to get the best track. I may also check the satellite configuration ahead of time, which may or may not affect when I go out, depending upon how accurate it is (Trimble has planning software for this)

If you run the same trail multiple times across days and months, you will likely find the tracks are similar shape but shifted in space or sometimes turns are missed.

If you don't like the accuracy of the watches and handhelds, then you can step up to the expensive gear and try running with that. You also have the option of rolling the trail with a wheel. Or running trails where someone has already done this.

The fluctuations that I find are miniscule in the grand scheme of things for distances over the course of a year of running.