@Anick-Bo0
I understand it is not a comfortable position when a negative Review.
I don't think your going to have a plumber emergency regularly, so that was just a minor unexpected inconveinance, for the Guest and the Host.
As to land area not standard even though the majority is, that is just a loophole. You have disclosed in your manual, I suggest even just a small garden fence around the area, to say not available.
The thing I would really think about is a 4 for minor inconveinaces and your buying them a drink didn't create a positive reaction. Some people are just generally complainers sometimes we have to reveiw our interaction created a negative response. The Guest did give a 4 but if serious issues one would expect a 2 or 3. I would look at the Review Catagories, that is Guest controoled independebt of Overall Rating. Sometimes all 5s and theb a 4 Overall , sometimes you will get a better picture if cleanliness is scored 2 there is a bigger issue then plumber using stairs.