outbound Voice cutting

HI,

we have a big problem with inbound call;
during all calls received in completly random mode the caller no longer hears the voice for a few seconds. at that moment there are no problems with the codecs or the rtp stream on the wireshark track; the only thing you notice is a loss of the "TX" network flow in transmission on the ETH0 ethernet card, from the graph in the dashboard. we hear the caller but he does not hear us, then the call restarts normally after a few seconds. we changed the virtual network card driver by installing a "T1000" vm ware but the problem persists.