1. your querry is not clear. (a) if it is "void contract" ab initio, then there is no necessity even for cancellation of sales deed.
(b) if it is "contigent to certain actions from vendor" , then purchaser can go for "specific performance of contract" and cancellation may not be feasible.
(c) Generally in agreement to sale, it is specified that there is title for vendor to sale & purchaser has satisfied himself about the same , at time of entering into contract--- hence there can not be case of breach of trust or misrepresentation involving criminal liability. Purchaser can treat the same as "voidable contract " & can rescind the same.
(d) It is advisable to ascertain the facts & reasons for necessity of cancellation and if deem necessary then cancel the same with mutual consents & terms.
(e) If cancellation is required due to sme problems with purchaser , then with due notice vendor can do the same,