Rectification of sale deed of apartment after 12 years

Dear Sir, I own an apartment which is 12 years old. I am planning to sell the same. I found there was an error in the sale deed entered between us and the land owner. There is a section where it says that the UDS land portion has been purchased by the nominee of the builder. Is this legally correct? We applied for EC and the land portion shows our name. Few buyers after wetting from their lawyers indicated that is a mistake and cannot be rectified by a deed. Please let us know how we can fix this error. Thanking you in anticipation of a quick response Lakshmi