From: Rabbi Moshe Sofer
To: Rabbi Yosef
A husband who had sworn not to nullify a get later produced two witnesses claiming he had nullified it before delivery. The Chasam Sofer rules the get is fully valid through three independent arguments: the nullification witnesses were contradicted by others (terei u'terei) leaving the wife in her presumed divorced status; the witnesses retracted under oath in a din merumeh case where their testimony had never been finalized; and the written document they signed lacks the status of a valid shtar. Esther bas R' Pinchas is permitted to remarry any man she chooses.
Source: Shu"t Chasam Sofer CM §4