Is the fast considered valid when in doubt about water entering the throat during ablution in Ramadan?

The Prophet, peace and blessings be upon him, commanded not to exaggerate in sniffing water into the nose (istinsḥāq) for a fasting person, for fear of water entering the throat. If a fasting person doubts that something has entered his throat, his fast is valid, and doubt has no effect. And if he becomes certain that something has entered unintentionally or without exaggeration, his fast is valid according to the preponderant opinion of scholars.