Devastate

Thanks again for your help, you were right, the solution does work, but only if the process is followed very strictly. I can see why others may have failed or stopped midway.
In my case, if I didn’t do:
downgrade to 4.0.41
factory reset at that exact stage
only use the correct command to bypass the wizard
then upgrade
it would break things badly (I had HTTP redirection to /dumaweb, SSL issues, Windows Update failing, etc.).
Regarding your question about the 24h disconnect:
Before this full process, I had hard disconnections every ~24 hours with no automatic reconnection at all ; I had to manually reboot the router each time.
Now, after applying the full method, everything is stable. It has been 48 hours without any disconnection or need to reboot, so for now it looks like the issue may be completely resolved.
What I’ve also identified is that the issue seems to be triggered specifically after performing a factory reset on firmware 4.0.540 or 4.0.645. After that, PPPoE auto-reconnection stops working correctly. Using the 4.0.41 reset + upgrade method seems to avoid that state entirely.
I’ll continue monitoring to confirm over a longer period, but this is already very promising.
Also interesting to hear you're running 4.0.645 successfully, that gives me confidence to maybe test it later, once I’m sure everything is stable on my side.

Thank you; I now know that the solution does, in fact, work for others, albeit with some bypassing involved. I have suggested the solution to others in the past, but I don't think anyone has actually persevered until the end.
I have promptly used the latest firmware versions, as they are released, with the solution. I am currently using firmware version 4.0.645. The only slight problem I have encountered, which may be unrelated to the solution, is that the '--' fails to load occasionally. This problem has only started to occur more recently, and it resolves itself after some time without any intervention.
One last question: do the 24-hour disconnects still occur but automatically reconnect afterwards, or do they no longer occur altogether?
 

From my testing, my solution only works if the factory reset is on firmware version 4.0.41. Firmware version 4.0.41 was the last firmware with PPPoE working. Any factory reset after that firmware will break it again.
The solution was to automatically reconnect when a disconnect occurs. I'm unsure whether it will prevent your disconnections from happening altogether.

The workaround I use is this .
I am able to successfully upgrade to the latest version with these steps, replacing step 3 with the latest firmware. This solves that PPPoE issue for me.

If its the PPPoE issue then you're only the second person to report it so not a widespread issue but it is being looked into. The internet dropping when you turn your PC off makes no networking sense whatsoever so I can't even begin to determine why that might be happening at the moment. The R3 WAN IP into the DMZ correct?

This.
I scanned through Reddit last night after you mentioned it, there's a fair few VM engineers / technicians that weighed in on the discussion and it seems to be an issue with their older wiring and systems apparently.
Weather I use the VM router or the Netdumer, the ping is the same 26+, probably doesn't sound much, but it's quite high compared to the 16 I was getting 

I use Firefox as my daily browser. If i leave the website for idle too long, the page changes to the screen below.
Is this some kind of issue with the forum as the URL does change in my browser because if I refresh, this page stays loaded.
https://forum.netduma.com/?app=core&module=system&controller=ajax&do=instantNotifications&csrfKey=7738584cb0f56afa861cdb32ebc7aee3&notifications=0&messages=0

I would like to suggest the following improvements to Hybrid VPN:
1. The ability to enable and disable the VPN connection per device rule.
2. The ability to have multiple rules per device.
3. The ability to apply the VPN connection to the entire network.
4. The ability to switch between VPN configuration files.
5. The ability to enable or disable a kill switch.
Most of these improvements would decrease the amount of time spent editing VPN configuration files and device rules.

No, it also interrupted the connection to the WAN during operation tonight. No resync or restart

I understand what you mean with 2 but that could get quite cluttered. I'll pass on the suggestions. 

Good job @Devastate thanks for helping out!

Yes thanks for clarifying, i was just checking as I only seem to get the Ireland, France and Netherlands servers in rivals and champs despite living in England, weird.

Thanks for trying to help; however, I am currently using bridge mode on a modem.
 
That's fantastic. Hopefully, the issue can be fixed and released soon.

May I also receive access to Early Access, please?