Unwanted auto calibration of Stryd

I have a Stryd foot pod and use the CIQ power field, as well as using it for speed. Distance is currently set to "indoor only" due to the issue I'm having.
Auto calibration is turned off and it seems pretty accurate with a calibration factor of 100.0. However I keep finding the calibration factor has changed - usually to something around 96 or 97. This is a pain when pacing intervals!
Has anyone else experienced this bug? I assume it's somehow auto-calibrating anyway, despite the setting being off. Grateful for any advice!