I have the same problem with my NC33 mkII 1988. I discovered this problem during the initial miles in 2011 when I found only two stables positions (wind on the side or wind on the back) and enormous difficulties to change from one position to the other.
My conclusion is that the boat should never bear too much sails, should never tilt on the side (humm, french is ‘giter’), 40 squera meter is sometime too much :-<
Latter I also came to the conclusion that the helm (the steel plate at the back of the boat) is very badly shapped (profiled ?) for a sailboat. I remember that Joel Rogale in Cherbourg did change it to a NACA profile (airplane wing profile).
Under conditions (not often by chance) with wind between side and back (135°) and light sea I cannot keep a track unless I force more water to run on the helm plate (read : I turn on the engine and run at 900 rpm).
Thus I will read your advices on this forum with extreme interest 😉
Who said ‘magic’ ?