I have two users.
One users booked a meeting room (resource) every two weeks, reoccurring every Wednesday at 2PM.
The other user did almost the same, same meeting room, but reoccurring every week at 2PM.

One user started the meetings last December, the second started in January.
When they booked they didn't get an error that the resource was already busy.

At the time the system was on GW8, now we have upgraded to 2012sp2.

People in the meeting request from user 1 see "their" meeting.
People in the meeting request from user 2 see "their" meeting.

If I proxy to the resource it only sees meeting 1.

I have tried gwcheck on the resource, no errors found.

What can I do to fix it, and prevent this from occurring again in the future?