I have a standard Holybro Pixhawk 1 on a quadcopter. The aircraft generally flies ok, but when descending, it wants to make a sort-of swirling motion on the way down. It does not change heading. It just rotates itself in sort-of a corkscrew on the way down. I am using the compass in the overhead GPS saucer with the Pixhawk compass turned off. I haven’t seen a quadcopter do this before. Any thoughts?