Hi @Hugh86
it's an issue about how guests understand the review system. Well, by the way, the review system might be an issue at all.
Your guests give you a rating in each of those six categories like cleanliness, ... but they give you overall rating, too.
It's strange that a guest rates you in each category 4 or 5 stars, but the overall rating is 3. Usually, in this case, Airbnb asks the guest during the reviewing process automatically if he's really sure to give a overall rating lower than the rating in each section. Because even Airbnb asks himself, where was the issue about your stay?!
An overall rating of 3 stars mean to me like 60% satisfied about the stay. So, what about the rest. Did you get any feedback from your guests??