I also did a calibration in the air and it seemed to work on my Inspire...I'm sure that if you are on perfectly level ground when you start the Inspire, that you shouldn't have the horizon tilt either.

I'm gonna try this asap. I've been having this issue since I got my P3P 5 days ago. It's been annoying. From laggy FPV to tilted horizon... I haven't been feeling all too great about my massive investment (over $2500) at this point.

Hopefully this works or I find something that does soon. I'm way too deep in the whole at this point.