@Elenita0,
Do you use more than one booking platform? (Meaning Airbnb plus VRBO or HomeAway or Booking.com).
(Which is perfectly fine. Many many people do that and it is not wrong in any way.)
Even with Instant Book, if you are *just* on Airbnb, then it should not be possible to have two conflicting bookings. If that did somehow happen, then you should be given a penalty-free cancellation.
However, if the conflict happened because you are on more than one booking platform, then yes, Instant Book can cause this sort of problem. There are some things you can do to help avoid it though.
(Synchronizing the calendars using a multi-platform manager, for example.)