Finstall
Reading he bits on Ghostrider it would seem his rudder inputs led to finstall. The fin is just a wing (quite a big wing) on its side and all aerodynamics apply. Once in finstall IIRC it could be recovered but at extremes the rudder could end up blanked and recovery virtually impossible.
Finstall was never mentioned during my time on the aircraft but I'm sure there is mention of it in Aircrew Manual. Having had the guy mishandle the Tac T/O EFATO in the sim I had a play and the sim reacted as advertised. No time to play with recovery actions as sim then exceeded movement limits and exercise ended.