Are you getting double booked on your google calendars? Don't worry, what might be happening here is that when you create a manual event, Google calendar sets your availability as free by default.
Let me show you with an example, let's say i'm attending a Developer conference on the 18th, and I'll create a manual event for it. Now, if you notice here in the more options tab, there is an setting here which is marked as free. And sometimes by default google calendar sets it as free.
Now what happens if the setting remains as free is that there will be a double booking if a booking is made during that time. This is because google calendar marks your availability as free even if an event is created for that time slot.
Now let's see what happens when I create this this event on the 18th, and leave it as free, also note that since I'll be at the conference the entire day, I'll leave this as an all day event.
Let's save the event and open up a booking page for one of my meetings connected with that google calendar account. Notice here that I am able to book a meeting on the 18th even though there is an all-day event in my calendar.
Now if I go back and set it as busy, and save it. And come back to my booking page. And I'll reload the page, you can see here that i am not able to booking meetings on the 18th. This is because google calendar has marked you as unavailable.
This why you should always ensure that you mark your manual events as busy. So that double bookings do not happen. Thank you