Hi , its not just FP . If using Uncast, then this issue can / will arise even if laying via a laptop. Basically in multicast, its a broadcast fire and forget paradigm. In Unicast , the ARP requests expect a response and hence the 'pause'.
Its the first thing I ask , cause I spent much time on this last year troubleshooting when I had mine setup as Uncast (I was set that way for me)