Like you, I am using another platform as well as Airbnb and through being here on the Community Centre for 3 years I have learned not to trust calendar syncing....it does work, but it doesn't. Many users report double bookings due to the failure of one platforms syncing system or the other.
For that reason I have specifically chosen not to be involved with calendar syncing. As soon as a booking comes in on one platform I manually block those dates on the other. I do have reasonably high booking rates getting around 12-15 reservations per month and I am having no issues doing it this way. Both platforms apps are downloaded to my phone so the whole procedure is quite seemless and no matter where I am I can attend to accepting and calendar blocking quickly and, my judgement hasn't let me down yet.
The Airbnb platform is much like the Boeing 737 Max8 aircraft. Way too much 'tinkering' is going on with the site programming, and when you start fiddling around with one aspect you are sure to create problems in another.
Karla, handle your bookings manually and you will leave these inept issues behind you.
I sometimes think we hosts are far more professional at what we do than Airbnb are at what they do!