I faced a simular problem with the Majestic Dash8 q400.
I am using
FSUIPC
FSiPanel
Saitek Pro Yoke with pedals and throttle quadrant.
With the FSiPanel you can do a test and it reported that my SLEW axis were having an issue, If I loaded up the plane with FSiPanel, the plane would just go spinning.
I solved the issue by re-calibrating all my attached devices ( Yoke, Pedals and Throttle quadrant).
Hope this info helps solving the issue.