Nighthawk Model# MR1100-100 - ethernet and internet connectivity

Nighthawk Model# MR1100-100 - ethernet connectivity 

Using Mac-mini: connection is shown, yet no traffic is shown with any app. Browser shows "no connection", mail does not load etc etc.

Router is set to both tether and charge, 5Ghz only. (single or dual does not affect the situation)

Mac is set to allocate the connection to Ethernet first, then Wifi etc. 
I have had wifi actually turned off on the mac, wanting to ascertain efficiency of the router via ethernet.

It does work on occasion, but have yet to figure out if there is a "special boot sequence".

If router is activated AFTER mac boots: Will not work.
If router is already active BEFORE mac boots: Will not work.
DURING wifi use, can sometimes get a response when mac system settings are changed to use ethernet as priority, but not consistent responses.
If the mac is put to "sleep", Ethernet connection fails.

If mac is running wifi and ethernet is prioritised and diconnected and then plugged in, a response can occur frm the router, but not always.

In all of these cases it is possible to see that there is an ethernet connection recognised by the Mac with the grren "connected to internet" indication 8/10 times.

Ethernet cable is brand new.

 
...so it really looks like a router hardware issue.

Please advise. I have had this device for 7 days now from EE (UK) as my main internet AP, so I really need this to be reliable.

LAST POINT:
Using wifi or the odd occasion when ethernet also works, the web-page build/response time can be up to 24 sec. It is never under 6 seconds.
This is both on wifi and ethernet.

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OS: Sierra 10.12.6

Router Model: MR1100-100

H/W: 1.0
Firmware: NTG9X50C_10.20.05.00