IPv4 name resolution - why does this get lost?

I have a two PCs on the same subnet, hardwired into the same router. Every night they timeout and sleep, Every morning my KVM software Microsoft's Mouse without Borders complains (on each PC) that it cannot find the other PC.

Both PCs have fixed (not dynamic) IPv4 addrs. The mouse software (which is used to cursor/cut/paste across multiple PCs using only the mouse and keyboard of one PC, operates on IPv4. Both PCs are configured so the software has the fixed IP associated to the name as backup to any dynamic name lookup. IPconfig shows the ipv4 values are correct. Both PCs seem to web browse just fine.

Some have suggested to disable IPv6, but that causes certain other software networking issues on the web.

So, to wrap up a long story, I came across a forum that hinted at an idea. I ping -4 at a command line on each PC to contact the other PC. SURE ENOUGH! As soon as ping sorted out the IPv4 connection and started showing reply packets, Mouse without Borders started working!!

What went on on in Windows to wake up IPv4 and how do I configure Windows to keep using it without having to wake it when the PCs come out of sleep? Yeah, I might put a script in, as a work around, but what's the real fix?

I'm guessing, someone here knows enough about netsh interface ipv6 show prefixpolicies to know if protocol priorities would fix this and how to use them.

Found this https://support.microsoft.com/en-us/kb/929852 which include a diagcab for setting IPv4 or IPv6 as higher prio. Seems to work on Win10 but not on my other Windows PCs (v7).

Here's a general network trouble shooting thread:

Resolve network issues

You can probably start at #4

Try to create this value: KeepAliveTime