Does a guest's complaint about the room defeat my claim for the unpaid stay?

A complaint helps the guest only if it behaves like a real complaint. The reason "services not rendered" works as a dispute reason is that it implies the guest raised a problem, gave the property a chance to fix it, and did not receive what they paid for. Every part of that sequence leaves evidence, or fails to. A guest who genuinely could not use a room usually reports it, asks to move, asks for money back, or leaves. A guest constructing a reason after the fact typically did none of those things, and the silence in your records is the most useful thing you own.

So the enquiry a judge runs is chronological, not emotional. When was the issue raised, and to whom. What did the property offer. Did the guest accept the offer, refuse it, or ignore it. Did they stay the remaining nights, and did they check out normally. A documented offer that was declined is close to fatal to the guest's story, because it shows you performed and they chose not to take the remedy. This is why front-desk notes matter more than owners expect. A three-line entry recording a complaint and what was offered turns a he-said-she-said into a timeline.