No answer I'm afraid but I can confirm the symptoms and the cause. It's definitely the Intel i217-LM chipset that's causing the problem when the PC's go to sleep.

INTEL ARE YOU AWARE OF THIS PROBLEM AND IS THERE A FIX? It is a REAL issue that has the potential to kill a network and, believe me, it's not easy to track down the cause. We have spent 30+ hours on investigations to nail this problem to your chipset and it would be nice to know whether there is a fix. It seems to affect machines from all manufacturers (Dell and HP to name two) so it's not a PC manufacturer problem, it's an INTEL PROBLEM. Please provide a fix ASAP.