There is a function that forces double-booking despite the rule I created to stop it in MS exchange Online. I’ve set Allowconflict off but, apparently, it did not do the trick. I also checked and double-checked the resource so everything should be in place to stop these unnecessary bookings. Advice anyone?
Hi @Flynn,
No worries!! 
I can able to help you. Can you please paste here your calendar processing setting using the below command
Get-CalendarProcessing -Identity "Calendar-Room-Name" | Format-List
So, that I can review it.
