A Rectification Deed, used to correct errors in a Sale Deed, can indeed be cancelled. Both parties involved in the original Rectification Deed must jointly execute a new Cancellation Deed for this purpose. While a Sub-Registrar cannot unilaterally cancel a registered document, they are generally required to register a Cancellation Deed if it's jointly executed by all original parties. Legal action in civil court might be necessary if parties cannot agree.