Smart-Flex reservations (previously known as Risk-Free Reservations) increase the possibilities of cancelling your reservations to encourage more people to book in your property. This means that guests can easily change their plans, which can lead to a higher number of cancellations.
Due to technical limitations on the side of Booking.com, it is recommended to disable Smart-Flex reservations in the Extranet. Otherwise, overbooking may occur.
Go to the article in the Booking.com help center to learn how to disable Smart-Flex in your property.