Firmware 4.5.3 BT not working with Vigor 2866!

So I have a pair of Vigor 2866's and when I upgraded them to the latest firmware of 4.5.3_BT, both of them just give a blank white screen when going to log in via HTTP/HTTPS. Ended up having to roll back to firmware 4.5.2.2_BT using the TFTP firmware tool and restore backed up configs to both of them! And yes, I tried clearing my browsers cookies/saved data. Trying to log in using a incognito window gave me the exact same result/problem. Also tried both Chrome and Firefox, same result.

Tried again checking the MD5 and SHA1 checksums match as advertised on Draytek's website, which they did, but same result of being unable to log in via web browser. Again having to roll back firmware.

I do run the HTTP and HTTPS ports on no-default ports as I have a publicly accessible web server running on port 80 and 443; but never had any issue before when it comes to upgrading firmware on my 2866's.

Any ideas? Anyone had similar issues?

I can't offer any great insight into your problem as the upgrade of my 2866Vac firmware from v4.5.2.3 to v4.5.3 went without a hitch.  I always upgrade from a downloaded firmware file, as you did.

Sometimes doing a factory reset before and/or after a firmware upgrade can prevent problems (and maybe also upgrade using the ".all" firmware file for good measure).  I've never needed to do this with my 2866Vac but I might have just been lucky so far.  Obviously you wouldn't want to re-enter all your settings by hand but you should be able to save them to a file first and restore them after the firmware update.  It's a bit of a nuisance to do this but it might be worth a try (if you haven't already).  The change log for 4.5.3 makes it sound like it's worth having.