I myself am experiencing router (2860ac) reboots every 5-6 hours since updating firmware v3.8.4.2. I never tried v3.8.4.1 or v3.8.4 - I came straight from v3.8.2.3. which was stable over many days. Have raised a ticket with Draytek, there are too many reports of router reboots from users on firmware v3.8.4.x for it to be anything other than a problem with the new firmware.

Just to add my 2p worth - I upgraded to 3.8.4.2_BT then found that my PPTP VPN would not then connect through (which I then read in the Known Issues about) so I downgraded back to 3.8.2.3_BT. I now get random reboots which strangely only seem to happen in the mornings generally within the first hour or so and then are OK until the next morning. Can't try upgrade again until they fix the PPTP VPN issue though.

I turned off the hardware accel. but that has made no diffence. I'm going to try a white BT modem again on LAN2 to see if that helps.

Rob