Running ZCS 6.0.8 RHEL5 64-bit

I have one user who is constantly getting duplicate address book entries. Several times per day, he will have up to 15 contacts in his address book that are duplicated between 2 and 60 times each. He manually deletes the dups and within a few hours to a day, it happens again. He seems to be happening to the same 15 or so. It doesn't always duplicate all 15 or the same number of times. This has been happening for months and is not the result of a recent upgrade.

He is using a Mac and maintains his address book in the address book on the Mac side (running Connector for Apple iSync 6.0.8). We haven't been able to nail it down to a specific function he does to cause this.

Can someone please lead me in the right direction as to how to resolve this? Is there a log file on the server that I can check to see if a specific address book entry is causing the problem?

Thanks for any help.