PowerConnect 8132F multicast problem

Hi,

I am using a PC 8132F switch and trying to test multicast. I found a strange problem. I have a device that works as the sender of multicast packets. And a server works as the receiver of multicast. They both connect to the 8132 switch. IGMP snooping disabled. 

The problem is that ONLY when the sender device is configured to use a specific MAC address (the device's MAC address, as source MAC), the multicast packets got forwarded out. If the sender uses any other MAC address, multicast packets won't be forwarded. However, even when the multicast packets are not forwarded, if I do "show interfaces counters" on the incoming interface, I can still see InMcastPkts increase with no errors. 

Any ideas? Thanks for help!