IP Subnet to internet routing fails 5x/day after latest 16.04 LTS updates

Since updating Ubuntu 16.04.02 LTS with all latest patches on 6/2, my subnet internet routing is failing 5x+/day for my Windows 10 machine. Unfortunately, Windows 10 is also a moving target, which also updated 6/2, about when this problem started. Bug report also filed with MS.

Why I think it's Ubuntu... When Windows 10 based web pages stop loading, email stops transmitting, and internet-based CAD licensing stops working, I can get everything working like new again by typing "firehol start", which refreshes iptables entries. So I suspect the issue might be related to either the Linux kernel or iptables.

I also see another bug dated 2-Jun-2017 for IP subnet routing, but that one is running on an ARM processor. Mine is AMD FX-8120, Ubuntu 16.04.2 LTS x64. The reported problem sounds similar.

I performed an IP Tables dump during "operating" and "not routing" states. I can't see any difference between the two dumps, but running firehol start clears the problem.

While in the "problem state", my Ubuntu server does have internet connectivity. i.e. Loading web pages on Firefox on the Server/router does work. On the "routed" Windows 10 machine, what doesn't work are; ping (internet), Firefox (internet), Thunderbird (internet)... From the Windows 10 machine what does work are; ping (server), Firefox (server apache web pages), Thunderbird (server imaps accounts). So the Windows 10 machine still has full server access over gigabit ethernet, but can't see any internet based services, where IP routing is required to succeed. "firehol start" restores routing until for a brief time when the Windows machine is busy accessing the internet. Routing stayed up all night when there was no Windows 10 internet routing activity. Resuming activity in the morning caused a quick routing failure.