I have come across an odd issue with the 2860ac, that was not present before 3.8.4 but is now. I've been using the SSL Web Proxy function (on the SSL VPN menu) to allow access to a LAN website from the Internet, with the 2860ac acting as an SSL server so the public connection is encrypted (using a signed certificate from LetsEncrypt). The LAN website requires login using Basic Authentication (hence the need for encryption), and the Vigor puts up a login screen to prompt for the credentials. Prior to 3.8.4, a successful login got me through to the website. Since 3.8.4, I get a 'connection reset' error in the browser.
Over the holidays, I put up & tested a LAN website that doesn't require authentication, and confirmed that it works properly with 3.8.4.2 when accessed through the Vigor in the same way from the Internet. This narrows down the issue enough, so I've reported a bug to draytek.co.uk
Anyone else hit this one?