Hi All
Hoping someone can help me with this weird issue... I've had an unlocked HG612 running for years after setting up with the great guides on here... however in the last few weeks my Hive heating developed a strange fault. Now I'm not sure if it's the HG612 but I'm hoping someone here might be able to help me troubleshoot as I've spent hours on to both Hive and Netgear without resolution.
The problem is that when I am connected to my local network (on any device, app or browser, ethernet or wifi) the Hive App wont let me have access - or if it does (as I seem to temporarily get access when some router settings are changed) it doesn't last long before I start getting errors. If i use mobile data or connect using another network from outside mine (say at work) I have access fine.

I was running a Netgear R8000 router but as a result of this I have splurged out on a Orbi system in the hope it might solve the issue (I was having some wifi problems as well with this and 2 x APs so this pushed me over the edge) but it hasnt.
So current setup is HG612 Modem with Netgear Orbi 850 doing the routing.
I've run through setting changes with Hive and Netgear helplines all to no avail, setup port forwarding and port triggers for what I am told are the ports Hive uses but again no joy - although this sort of setting change does seem to allow proper access for, say, 5 to 10 minutes before it all goes back to being broken strangely.
The Hive 'dashboard' sits on the Hive server I believe which then speaks to my hub... which I assume is all fine as I have access from outside my local network no problem.
So it seems to be either outgoing or incoming traffic to and from a device, connected locally, trying to talk to the Hive server and get access to my dashboard.

Is there anything setting wise on the HG612 that could be the cause of the issue?
I've had my BT home hub connected with the Orbi in AP mode and this seemed to work fine, but obviously this doesn't narrow it down between the modem or router really.
Any help much appreciated?