I was finding the user interface on the Vigor2862 was incredibly slow.  Pages would take many seconds to load, if at all.

I then switched from https to http access and the response is now fine.  

No special certificate for https;  Safari on Mac as the browser.  Since management is only local, this doesn't matter to me that much, but I wonder if anyone else has observed this and has a solution.

Firmware is 3.9.9.9_BT but I was having the same issue with previous firmware.  As an aside, with 3.9.9.9_BT and SSL VPN disabled, I now no longer see random WAN re-connects.  

After my last post, as an experiment I regenerated the self-certificate (although the previous one was not expired).
UI response still slower than with http, but was better initially.

Hi John,

Check your “System Maintenance >> Management  /  Management Setup - TLS/SSL Encryption Setup” try enabling only ‘TLS 1.2’ and disabling ‘1.0’ & ‘1.1’…

See if that helps. This worked for me when connecting from several different browsers.

Thanks for the suggestion.
Already was set to ‘TLS 1.2’, so don't think that's the culprit.
Interestingly, with the same settings my 2865 router UI is fine.
I do wonder whether the 2862 is perhaps overworked - runs about 16% cpu and 95% memory.

Oh ok, but are the 1.0 & 1.1 disabled, as they are more the focus of the slow down than just having the 1.2 enabled. When the 1.1 & 1.0 are also enabled, I see slowness and refusal of connection even! 

I agree with you though, the 2862 is the oldest router I personally manage over a collection of sites, and can be a bit slower than the rest, but has always been one of the most stable and faithful, if that’s something you can still say about the DrayTek gear.

Yep, TLS 1.0 & 1.1 both disabled!