Big variation in steps per mile

[KG27]

Inspire 2, my settings include no GPS and set your own stride
Until recently, I had a fairly consistent 2632 steps per mile. Now, it ranges from 1667 steps per mile to 3656 steps per mile. A little variation would be logical, but a 2000 step difference is a bit off. 

Any idea why this would occur?

[JohnnyRow]

Not sure these affect your issue, but to clear up 2 misconceptions.

I'm fairly sure you can set your own stride for any Fitbit device.  On phone app from Today screen:

days of exercise tile > gear icon near top right > Stride Length

Also you can use connected-GPS, connecting to your phone's GPS.  You can read more about this starting on page 35 on the Inspire 2 manual (pdf) .

[KG27]

Those aren't misconceptions, those are my settings. I don't want GPS turned on and I set my own stride length. 

[JohnnyRow]

Sorry, I misinterpreted or misread.