I also think that the cable (or one of the cables) for the left aileron burned through due to the engine fire. The airstream / lift will then push the aileron all the way up.
That would make any further right turn more or less impossible. Full right aileron would just have given them a balanced situation. Of course both ailerons all the way up will add quite some drag.
Great airmanship to keep it flying and not crashing doing a snap roll to the left.