In using the GPS in Astrotracing mode, there is star tracking around the extreme edges and corners. When you eliminate/crop these tracks, you wind up loosing at least half the frame. The error increases with tracking time (from a minute to the 5 minute limit) on wide angle lenses. The only way to reduce the error is to not track beyond a minute or go to a substantially shorter focal length like 30mm.
This does not occur when using either an equatorial tracker or even a barn door tracker, with wide angle lenses (10 to 30mm). This points to an accumulating error within the system (even after a successful fine calibration). Various folks have measured errors in the electronic compass up to +/- 15 degrees. So, it appears that Pentax is simulating a barn door tracker computationally. And since there is no alignment process to the north, Pentax is using the compass to align mathematically to the north in order to then perform the planer shift of the sensor for tracking purposes. AstroTracing is too nice of a feature to be left to this type of error. This needs to be fixed. This error can be demonstrated across the K5, K5II/IIs, K3, K3II and the K1. I also assume that it is present in the K30, K50, k70, K-s1/s2.