Airbnb & Booking.com calendars not syncing

Good morning,


I own an apartment which I rent on airbnb. I recently also started advertising it on booking.com. 


I synced the calendars on both advertising platform, but I have consistently had double bookings - so much so that I have had to temporarily snooze my listing on bookings.com


I have checked and rechecked the calendar sync and can not find the issue. 


Are you able to please assist me?