Legally (or as it stands in the UK) the Guests' have to make any complaint during their stay at the property, otherwise whatever the reason (for the complaint) cannot be attended to, or the Guest be refunded, once they have left the premises.
Having said that, the only way I could see to stop them making a claim, when you had verbally advised them of a fault (or anything else you wanted to mention), and where they had accepted your verbal advice, would be to either send an email to Airbnb Support straight away to advise them of what both you and your Guests' had said, or - far more "secure" for you - would be for you to get your Guests to sign a piece of paper (aka document) confirming that you had advised them, and that the matter had been rectified to their satisfaction! - again to be signed before they leave your property.
Although the latter method may well be considered to be contentious, one also has to consider that most Companies where their workers have undertaken work on your behalf, will require you (the customer): to sign a document to confirm that the work has been undertaken, and that it is to [the satisfaction of]... (or, once again, that is the situation in the UK).
Perhaps more guidance from Airbnb would prove beneficial in such incidences as mentioned?