Rectification and registered owner in possession
71The title register shall not be rectified so as to affect detrimentally the title of the registered owner who is in possession unless
(a)
such owner had knowledge of the omission, fraud or mistake in consequence of which the rectification is sought, or caused such omission, fraud or mistake or substantially contributed to it by this act;
(b)
the immediate disposition to him was void, or the disposition to the person through whom he claims otherwise than for valuable consideration was void; or
(c)
for any other reason, in any particular case it is considered that it would be unjust not to rectify the register against him.