I added the 8168 DKMS driver, added r8168.aspm=0 r8168.eee_enable=0 pcie_aspm=off loglevel=3 to kernel settings and removed the no longer appropriate "hardware-irq-coalesce-rx-usecs 0" from interfaces.
I ran it a bunch yesterday and never saw the error so I have high hopes this was the problem.
Thanks once again for your help Pete!
Its amazing the difference when the right driver is installed. The 8168 driver really should be part of the default kernel. I've been cofiguring a PC with the R8111 with a Mesa card for the last couple of weeks. The only EFR I've seen is when I power off the Mesa card with Linuxcnc still running.
This computer was the reason why I went looking for solutions a couple of years ago and since then many others have chipped in with enhancements.
