|This sounds like it could be a NIC (network interface) issue. To isolate the issue, you could plug a laptop or something in instead. Just set the laptop on top of the printer, plug in using the cable from the printer (ie: unplug it from the printer, plug it into the laptop) and give the laptop the same IP address as the printer.|
Start a continuous ping from another computer and one from the laptop to something else. Let it sit for 30 to 60 min's. If it hasn't lost connectivity, it's a pretty safe bet the issue is the printer's NIC.
If it does, then you need to test all cables between the printer and the other end and then test the interface that cable plugs into at the opposite end from the printer.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.