Guests complaining about bugs

We are in Pacific North West, have a Airbnb suite in our basement, basically an ensuite room with kitchen in the basement of our house. And we have these European guests complaining about bugs in the suite. Not like bed bugs, but just normal backyard small critters that we find in our own house from time to time.

We have never had guests complain about bugs in the suite, and we have 50 reviews with 4.8 stars. Do other hosts get complaints about bugs? Is this a thing? I mean I hate bugs too but I wouldn’t blame the Airbnb hosts for bugs being in the suite?

And just for my future information, is there anything I can do to prevent bugs entering a basement suite?