Beagle,
Methinks you're onto something. The gyro is a possiblity. Just to think aloud: If I need to yaw right to adjust a crabbed approach prior to landing then the force would be on a right turning prop (as seen from the cockpit as most are in 0 ATPL land anyway) would be precessed 90deg clockwise and result in a nose down. It is a little tenuous as the prop will be idling by that time and so the gyro effect will be minima, but it fits otherwise.
