Weird issue with Exchange 2010 Room Mailboxes - allows multiple booking of the created meeting rooms

Hi,

we are facing weird issue with Exchange 2010 Room Mailboxes

it allows multiple booking of the created meeting rooms.Sometime we are not getting acceptance or declined mail but and we could see our meetings has been booked at slot.

for e.g.
User A booked room1 with weekly recurrence for time 4pm to 5pm., and User B made his  booking other day,without realizing that user A meeting is exists.

Neither of user A nor user B got declined/rejected emails.

please sahre guidelines if anyone known to this issue.

Note - Allow Conflict booking is disabled already :) but still have issue

Thanks,

NPratik