Also, is your S2 and PC connected together via two Ethernet cables to your ISP's Router?  It's much more reliable to connect Skimmer PC and S2 to the same external 1Gbps Ethernet Switch, like a Negear GS105, then connect the Ethernet Switch to the Router.  That way, when your ISP updates or reboots your router, the Skimming will carry on even while the Router is rebooting, because once connected, the PC and SDR communicate directly with each other through the switch instead of through the Router.

Also if you're using CAT5 cables rather than CAT5e or CAT6 STP (shielded twisted pair) there could be Ethernet reliability problems if using 1 Gbps devices.