microsoft office 365: double booking problem in the exchange room resource

I am working on a double reservation problem in which room calendars seem to allow meetings to be booked at the same time as other meetings. The calendars themselves seem to have the correct settings, and I can't seem to recreate the problem myself; however, I know it is a problem, since this problem has arisen once a week during the last 3 weeks in separate resource mailboxes, with different people.

This is a hybrid exchange configuration. Room calendars are created in o365, they are not synchronized.

Currently I have an open case with Microsoft, however, they have been closing the case for not being able to recreate the problem on demand.

Is there anything I can try?

Thanks for any additional information.

Resource Mailbox Details

get-mailbox | Get-CalendarProcessing | FL

AutomateProcessing                  : AutoAccept
AllowConflicts                      : False
BookingType                         : Standard
BookingWindowInDays                 : 365
MaximumDurationInMinutes            : 1440
AllowRecurringMeetings              : True
EnforceSchedulingHorizon            : True
ScheduleOnlyDuringWorkHours         : False
ConflictPercentageAllowed           : 0
MaximumConflictInstances            : 0
ForwardRequestsToDelegates          : True
DeleteAttachments                   : True
DeleteComments                      : True
RemovePrivateProperty               : True
DeleteSubject                       : True
AddOrganizerToSubject               : True
DeleteNonCalendarItems              : True
TentativePendingApproval            : True
EnableResponseDetails               : True
OrganizerInfo                       : True
ResourceDelegates                   : {}
RequestOutOfPolicy                  : {}
AllRequestOutOfPolicy               : False
BookInPolicy                        : {}
AllBookInPolicy                     : True
RequestInPolicy                     : {}
AllRequestInPolicy                  : False
AddAdditionalResponse               : False
AdditionalResponse                  :
RemoveOldMeetingMessages            : True
AddNewRequestsTentatively           : True
ProcessExternalMeetingMessages      : False
RemoveForwardedMeetingNotifications : False
IsValid                             : True
ObjectState                         : Changed