Thanks for responding, BKO.
First, my wiring is set up just as you describe. I've used this in other setups with the Spark, Photon, arduino with "success".
I'm using this to track the position of a solar panel, and drive a 12vdc motor to move the panel to the 'correct' position. I read the pot, drive the motor a bit, read the pot. And repeat as needed, then goto sleep for 30 minutes, and repeat the process.
Occasionally, the motor would drive the wrong way. Checking the serial.prints, my reads would show counts being inconsistent with expectations. That led to my search of the forum.
Your comments seem to indicate that the problems in this thread have been addressed.
Right now, my project is a messy hack on my office desk. however, after setting up a second photon and making a test setup, I found the same issue, and 'fixed' it by reading 3 times for an average, with 250msec between reads. I've incorporated the fix in my project code,thus avoiding the sample rate issue.
As aside note, there appears to be no examples of how to issue a sample rate adjustment in the reference docs.
So far, my project is performing as expected.