Yevamot 110B

חולץ לא! לא, בפקחת ואחר כך נתחרשה.

but no, he may not perform ḥalitza. The Talmud rejects this: No, it is referring to a halakhically competent woman who later became a deaf-mute, and ḥalitza performed by a deaf-mute does not have the power to undo a levirate bond that is valid by Torah law.

תא שמע: שני אחין פקחין נשואין שתי נכריות, אחת פקחת ואחת חרשת, מת פקח בעל החרשת, מה יעשה פקח בעל פקחת? כונס, ואם רוצה להוציא יוציא. מת פקח בעל פקחת, מה יעשה פקח בעל חרשת? או חולץ או מייבם.

Come and hear proof from a baraita: Two halakhically competent brothers are married to two unrelated women, one who is halakhically competent and one who is a deaf-mute. If the halakhically competent man who is the husband of the female deaf-mute, dies, what should the halakhically competent man who is the husband of the halakhically competent woman do? He consummates the levirate marriage with the deaf-mute, and if he later wishes to divorce her, he may divorce her. But if the halakhically competent man who is the husband of the halakhically competent woman dies, what should the halakhically competent man who is the husband of the female deaf-mute do? He may either perform ḥalitza or consummate the levirate marriage.

מאי לאו: מדהוא פקח מעיקרא, היא נמי חרשת מעיקרא, וקתני: כונס אין, חולץ לא! מידי איריא? הא כדאיתא והא כדאיתא.

What, is it not the case in this baraita that since he is halakhically competent from the outset, one may presume that she is a deaf-mute from the outset as well? And it is taught yes, he may consummate the levirate marriage with the yevama who is a deaf-mute, but no, he may not perform ḥalitza to her, thereby indicating that ḥalitza cannot be performed even though as a deaf-mute from the outset, she is a yevama by rabbinic law and not by Torah law. The Talmud rejects this: Are the cases comparable? This case is as it is, i.e., the husband is competent throughout, and that case is as it is, i.e., the wife was not a deaf-mute at the outset.