Overlap problem in recorded calls

I use AAH 2.8 as my IPPBX and I am making calls through SIP using G723 and G729. Our company is a callcenter and several phones are needed to use recording funtion because of our clinet’s requirment.When I make calls the quality of the call was great but when I hear the recording of the calls made that was horrible, the sentences were overlapping. I think it isn’t our machine’s problem since I upgraded it before. Can any body help my in that?Thanks~