What is the ruling on the fast of someone who broke their fast for six days, which they recently made up, then discovered an error in their phone's timing, raising the possibility of having eaten a few minutes before Maghrib or after Fajr, knowing that they rely on their phone because they cannot hear the Adhan?

If it is merely a doubt about a mistake occurring in worship after its completion, then it should be disregarded. The fast is valid, and there is no need for a make-up. However, if certainty is attained regarding breaking the fast before sunset or eating after dawn due to a mistaken belief, the majority of scholars hold that making up the fast is obligatory. Sheikh Al-Islam Ibn Taymiyyah, on the other hand, chose the opinion that making up the fast is not obligatory, and his view is strong in terms of evidence, even though making it up is more cautious and more absolving of responsibility.