When you establish a VPN the packet will be different format to normal. In general the packets are either TCP or UDP, but PPTP uses something called GRE (Generic Routing Encapsulation). See VPN Tunneling Protocols for pictures of the packet formats.
My guess would be that something in the firewall doesn't like this packet type and so it simply crashes when one passes through.
I wonder if moving a device temporarily to the DMZ would prove that? Not that it makes a lot of difference as BT don't seem to be listening so won't know what's been proven by the "guinea pigs" with the Smart Hub.
I have the same problem with the HH6 not working with VPN.
Luckily, I hadn't returned my HH3, so I have reconnected it, as I can't afford to be without my work VPN, as both my wife and I need it for when we work from home.
Btw, I was also told by BT help that they don't support VPN and then asked if there was anything else they could help with.
unbelievable poor service.
If you can stand the pain I would go back to BT and make the point I posted in message 19. The Hub is not supporting a VPN, it is being asked to NAT (Network Address Translate) and route IP traffic of a particular type i.e., GRE in the case of PPTP, and when doing so it crashes.
In message 5 and message 10 we've had comments that this is being fed back to the hub team. Any response from them yet? Also can we get a statement about the hub "not supporting VPN". As I mention... the hub is not supporting VPN.
I've got exactly the same issue using a HH6 and Windows 10 VPN client to connect to my work systems.
The HH6 reboots as soon as you try to pass some traffic (i.e. do *anything*). The HH5 is stable as a rock (although it had issues in early firmwares)
Im using the HH6 on a PlusNet broadband connection, so can't moan at BT directly; but I work in IT and agree with what people are saying on here - this is definitely a HH6 issue (possibly with the firewall; I haven't tried disabling that entirely yet)
exactly the same problem here, brand new smart hub - work lappy on Windows 7 and every time i try to establish a connection it causes the router to lose connection and flash green and orange.
unfortunately i sent back my old HH4 and am now left with connecting to work via iphone.
i know it's a consumer service, but it used to work on the previous non-infinity service, so i had reasonably expected to retain this functionality..
please get this sorted out soon, at the least give us a time scale for a fix or work around!