I did a video recently about this

Yes, the network is not setup properly (no fixed IP address)
 

I get command not found for some reason 

It sounds like the maybe Ethernet on the host has power management or enabled or something similar

what does:

ethtool --show-eee [ethernet device name]

report?

[ethernet device name] is the name of the Ethernet device connected to the 7I76E,
something like eth0 or eno1. You can get the device name from a the results of
the command

ip a



 

This problem has always been there, it is a new build I just completed last week and I have gotten this error from the start.

OK, the /INIT LED is illuminated on the 7I76E which means this is not a 7I76E power issue
but either a host or 7I76E network issue. (The /INIT LED indicates a watchdog bite)

Is this a new problems or has it always been there?

I disconnected all power supplies except for the one powering the mesa board and I still get the same error every 45 seconds. 
These are the lights on the mesa board 

When is disconnects, is the init light illuminated on the 7I76E?
 

I turned everything off except the PC and it no longer disconnects on its own and it doesnt show my mesa connection. But when I turn the mesa board and the machine on it starts disconnecting again every 45 seconds. So now I think you guys have a good point and maybe this could be hardware related.

Also make sure all power management is disabled on the host PC
Similar issues can come from Ethernet (EEE) or PCIE power management

I had a problem with a Mesa board disconnecting a couple years ago.

Turned out it was a bad/weak DC-DC power supply.  Voltage would drop intermittently, causing the Mesa to reset and I'd get the 'error finishing read' nightmare.  Looked like a network issue, but @PCW helped me diagnose it as a power problem.

Maybe double-check whatever is powering the Mesa and see if it's dodgy.

I did not try another LAN cable.
The machine and PC are grounded properly.
I dont have a DVM at the moment but as soon as I get one I will measure those.
I believe this is a software issue because even with qtplasmac not running I get the disconnected error every 45 seconds