Did they indicate what it was about your configuration that they thought was causing the issue?

No which isn't particularly helpful. Rebuilding yesterday from scratch it seemed to be after the VLAN section was populated with TAG ID's and port assignment when it then went unstable and started rebooting again on any form of interrogation. I backed up as far as I'd got and then downgraded and re-installed the backup prior to factory resetting, all is now working fine again back on v4.3.3.1

People on here have reported upgrading with the Taiwanese generic English version rather than the specific UK one and not having issue. I suspect it's when certain features of the Router are being used where the bug is which then causes the instability.

Yes I have tried both the UK and Taiwan downloads with the same problems. At least somebody in Draytek is aware that there are issues, thanks to your efforts.

On the unit you've had issues with were you using VLAN tagging and how many subnets were in use? Mine has 6x LAN subnets active with three VLAN tagged plus 27 active LAN to LAN VPN's.

Things seem to have gone a bit quiet with the person I was dealing with at Draytek on the support side of things since saying the issue is configuration related on my part. I've now put this back to him and closed that loop in confirming the issue recurs even with a clean rebuild on v4.4.5 so hoping it will get investigated a bit deeper.

I have 5 subnets with 3 of them tagged. No permanent VPN's set up. just connection available for occasional dial-in users.

Thanks, clearly it's not more widespread as Draytek would have received many more complaints so wondering if this is multiple subnet or VLAN related where implemented? I'll feed this back to them this coming week and see if I can get them to show more interest.

I'd like to hope support staff may occasionally browse this forum too but not so sure?