When your phone or pad is only detectable by one tower, that tower estimates your position based on your signal strength.
I’m going to make a wild guess that you bounce around back and forth in a pretty much straight line. If you look up your phone carrier tower locations, you may find that one of the area towers is in the direction your are jumping back and forth.
Places like valleys, being inside a big manufacturing buildings or any thick walled buildings can block your gps signal from area towers and the one tower that can detect your signal is estimating your location.
This happens to me at work when I’m inside the manufacturing building. I get bounced up to a half mile in two directions in the direction of the second closest Sprint tower. My workplaces steel walled and roofed building along with two other manufacturing buildings on the street block the line of sight Sprint tower just a mile and a half away. The Tower about 4 or 5 miles to the north has kind of an open space from my desk location and estimates my distance. My google map also shows my bouncing.
Try checking your phones location settings and see if it has a feature that uses nearby wi-fi or blue tooth to pin-point your location. This stops the bouncing for me. This is the android phone settings example.
Trying to be an added help for @Ned.