Virgin M600 -> Netgear Nighthawk slow wifi

[WBrook]

Just upgraded from M350 to M600 broadband with Virgin. Virgin Hub 4 is set to modem mode. Cat 6E cables used.

Speeds are topping out sub 300 when connecting to the R8000 via wire and wifi.

Speeds directly out the Virgin Hub 4 (in router mode) are around 600 (wired and wifi).

Speeds with the old Hub 3 were the same at sub 300 even after the upgrade from M350 to M600, hence I called virgin who upgraded me to the Hub 4. They couldn't identifiy the issue, and I guess it isn't really their place to.

Any pointers as to why the R8000 is causing the slowdown, and how I could fix it would be  very much appreciated.

[WBrook]

Just to add...

Firmware Version
V1.0.4.76_10.1.82

qos, traffic monitoring, access control, and parental controls are disabled

[plemans]

Even though access control, traffic monitoring, parental controls, and qos are turned off, were they ever enabled? 
If so, factory reset the router and reinstall it. Those services disable ctf (needed to hit gigabit speeds). And I've seen it not get re-enabled even after those services were disabled. 

So if you have, try a factory reset. 

[WBrook]

Thanks for the tip. I did enable and disable some of the options in the hope that this might kick it into action. The router restarted each time. This made quite a difference to the speed (up to about 500) but I’ll still give the factory reset a try too. Thanks!

[FURRYe38]

Be sure to save off a back up configuration to file for safe keeping. Saves time if a reset is needed.
https://kb.netgear.com/24231/How-do-I-back-up-the-router-configuration-settings-on-my-Nighthawk-rout...

[plemans]

Backups are always good to have but if you're having issues, a backup can sometimes have the old/bad setting causing the issues. 

so worth it to have but if your having an issue after a firmware upgrade/downgrade, I'd avoid them. 

[plemans]

@WBrook Furrye38 just likes to get in on everyones posts advising for backups. They have their place but aren't always a good thing.