There's something going on with AFP and SMB being used simultaneously. You didnt say anything about your scenario except its broken but I believe that the problem is on the OSX side and not FreeNAS.
I can't say much more because I ignore AFP problems out of habit because:
1. Apple is abandoning AFP
2. You shouldn't use multiple protocols on the same files simultaneously unless you like file corruption
3. AFP only works on OSX devices and the *vast* majority of users are not 100% Apple fans.