On my first flight I was getting the fish bowl effect, when I put the copter i forward motion it started going more in a 30 degree off center direction. After about 30 seconds of this it locked up and everything has been fine since. My theory is the issue may be in the compass data doing some type of self correction off the GPS to magnetic compass deviation.
I have had this issue with my WKM after the 5.16 upgrade. At that time is was so bad I thought the unit was bad, eventually I learned if I off set the compass by doing small test with forward flights and seeing the direction the copter would fly, I could dial it in by simply turning the in the compass unit in the opposite direction of the drifting motion. In turn you are off setting the correction needed from the actual error being caused by the deviation.
If you look at my compass on my WKM copters you will notice them pointing about -15 degrees off straight forward, where I live the magnetic deviation is about -11.
Considering the Inspire does not allow you to offset that compass manually my thought is leaning towards the FC needs to confirm the correction and it can not do this until it gets some type of consistent GPS Data; Movement is needed to derive this data, once this happens it then is able to lock itself in.