Channel meeting doesn't book objects

Dear community,

Recently it came to light that some objects (meeting rooms) where booked double. We recreated this and found out that while booking a room / resource within the channel meeting it shows the availablitily, but doesn't actually book the object. In Outlook (regular meeting) it would reply with auto accepting/declining the meeting. In the channel meeting it doesn't. The user is not aware of this and finds out at the moment of the meeting that it was later booked by someone else in a different (regular) meeting.

I understand that this has to do with policies, or hiding the group in the Global Adress List. Any suggestions on where I should look?

Kindest regards, Ruben