What should I do when I feel a very light bubble of air exiting from the anus during prayer, knowing that I do not hear any sound from it, and must I interrupt the prayer and repeat it?

The emission of gas (farting) invalidates ablution, whether it has a sound or not, if you are certain of its emission, even if it is a small amount. As for doubt, it is not to be heeded. This is supported by the hadith (definition) of the Prophet, peace and blessings be upon him: "He should not leave (his prayer) until he hears a sound or perceives a smell." This hadith emphasizes a great jurisprudential principle that things remain on their original state until the contrary is certain, and an incidental doubt does no harm. So, whoever is certain of purity and doubts about its invalidation, remains in a state of purity. If you are not certain about the emission of gas, what you experience is a whisper (waswasah) that should be ignored, and you should not interrupt your prayer. However, if you are certain, then ablution is invalidated and the prayer becomes void if it (the gas) exits during it. If its emission is continuous, then if it stops for a time sufficient for purification and prayer, wait for this time. Otherwise, you are in the ruling of one with incontinence, and you perform ablution for each prayer after its time has begun and pray the obligatory prayer and whatever you wish of supererogatory prayers.