@Julia3080
As this is a failure of the guest, next time do not decline, but ask them to retract the booking request.
You can easily check yourself for sure of dates are OK to book by simulating a booking on your own listing.
I did this now and although dates seem to be available, they can not be booked
There seem to be a issue with the dates.
So as alternative you can sent the guest the booking by special offer.