How can one respond to those who find problematic the discrepancy in the Prophet's (peace be upon him) sayings in the Hadith of Al-Jassasah regarding the place of the Dajjal's emergence, where he mentioned the two seas and then denied that three times, pointing instead to the East?

The aforementioned hadith is in Sahih Muslim and presents no problem. Scholars have addressed the claim of a problem by explaining that the Prophet’s (peace and blessings be upon him) statement: "Behold, he is in the sea of Sham, or the sea of Yemen – no, rather, from the direction of the East, what is he?” indicates that he was hesitant in specifying the Dajjal’s location, or he intended to keep it vague for the listener. Then he negated that and confirmed that he is in the direction of the East. The word "ma" (ما) in his statement "ma huwa" (ما هو) here is an intensifier, not a negator, or it could be a relative pronoun meaning "that which," or a negator meaning "he is nothing but in it." It is also possible that this was an ijtihad (independent reasoning) on the part of the Prophet (peace and blessings be upon him), and then revelation clarified the correct answer for him. His ijtihad is permissible, and even if he made an error, he would not be left to persist in error.