How do you deal with guest that ask to leave the hotel with a full refund when some minor issue happen to their stay?

Hi all, I have a recent guest, some minor leak happened during their stay, because upstairs guest let the water from shower got out of the tub. the issue was immediate rectified and they were refund of half day stay. But now they are asking to leave with a refund for the remaining days, they have 8 days remaining and purchased non refundable room.

How do you deal with situation like this? what's your thought.