I've now put my 3900 back into the data cabinet to give it a chance , got the latest RC firmware , so far seems ok

Some features on the 3900/2960 don't seem as good as the other draytek devices like QoS, Load balance etc

Would be helpful if you state specifically which features need enhancement, thanks.

Were should I begin ... lol

1. Firstly the Soft Reboot doesn't work even with firmware upgrading, it looks like it reboot on the Web Gui but later in the day dhcp etc. does work, I have to put my hand to the back of the cabinet and switch it off and back on.
2. I've tried different load balance for the 3 WAN/ADSL lines via Draytek Vigor120's but internet is slower than when I had the 2830Vn in play as per examples =
Firstly we have a networked credit/debit card machine which instead of taking 6 - 10 seconds to get authorisation it sometimes fails or after 2 attempts takes 25 seconds ( total duration is over 2 minutes )
when browsing the internet , the progress bar sticks so have to re-press for the page you want or refresh till it eventually arrives
Our PMS software takes longer to load on all machines as they utilize the internet to get updates etc.
3. trying to load the Vigor3900 admin page takes longer than expected 10-15 seconds, and when logged in the main status page is all bonkers, and moves on its own for system information etc
4. currently setup LAN1 [ 192.168.1.4/24]to use only WAN1 and Lan2 [ 192.168.2.1/24 ] to use only WAN3, and Download server on 192.168.1.3 to only use WAN2
5. about every 5 days the DHCP stops responding to requests so devices don't get a ip and so have to do a cold start on it which takes 10 minutes till working again
6. I tried using the bind IP to Mac but any device I gave a static IP to didn't work for internet , yet could see everything on the LAN, for example of LAN2 there is a guest desktop that has to be 192.168.2.3 so that untangle server [192.168.2.2 ] will let it pass with out needing a captive Portal page user authorisation , however giving it a static in Vigor3900 made the desktop have no internet , I removed it of the vigor3900 and switched of dhcp for lan2 and put dhcp on the untangle server for all LAN2 devices and now guest network is faster and more reliable than the LAN1

that's so far of what I can say at this moment

Hardware - 1.0
Firmware - 1.0.6.1_RC3a
Revision - 2021

Sent another email draytek support since the last two have been ignored.
The annoying thing the upnp is easy to replicate. Plug the webcam into the lan and try and access the webcam by it wan ip address and you'll get page cannot displayed. Fire up vpn and the url will work. On the 2920 the wan ip works without the need for vpn.

Trying to give the 3900 time to be resolved or possibly look in the mikrotik CCR1036-12G-4S

Got a reply back from Draytek and the latest firmware local upnp is still broken and the latest firmware so it's been passed back up the line.