Strangely enough, I have experienced something looking similar on Flight Safety' simulator the other day. We were simulating a "collective drive" situation with a jaming after the mixing unit; (rudder pedals inefficient and linked to collective) Everything was going not too badly at about 130 kts untill I slowly tried to reduce speed to about 80 kts for an IMC let down. For some reason everything went messy from here ; speed reduced to about 60 Kts, and when I tried to increase it again ,I had a shard nose up motion with (I believe) a left yaw I couldn't counter (collective drive situation) I cannot tell if the yaw then reversed the other side (I was IMC)
It ended up quickly in a simulated crash, with 3 pairs of staring wide eyes,and adrenalyn pumping...in the darkness of this diabolic box. Frightening !
But is the simulator faithfull enough to simulate situations at the edge of flight enveloppe ?