Hi Bailey - the rejection letter explains that a rectification of the title is inappropriate. When a legal deed has been registered you can't then seek to rectify the situation through a deed of rectification. You have to do a further transfer for example.
Looking at the Deed of Rectification it appears to be trying to replace/amend the plan used on the now registered Transfer. That's not now possible so if the wrong land was for example transferred and registered in order to rectify that the now registered owner would need to transfer land back.
The rejection letter does not state the type of transfer, TR1 or TP1, but simply that a transfer is the only way of putting it right.
Our PG 39 explains how and when rectification might be possible and section 1.2 is specific guidance on the above
Practice guide 39: rectification and indemnity - GOV.UK