Just spent the night going back and forward through backup images, the problem is definitely after v6.1.298.1564. Rolled my PC back to 27/12/16 and all is working great, update to latest Adguard and all broken. No other changes have been made to my PC in that time, as soon as the new version is installed the trouble begins. I,ll stick with the older version for now but if the problem persists in newer versions I,ll go back to Admuncher. Also the router page loading issue is way way older than this thread, I had that way last year and its been around to some degree through the versions since
Honestly, the only way it will be fixed is if somebody experiencing this issue gives one of the devs remote access to reproduce the issue and see why it's happening. Otherwise if the devs can't reproduce it, it may indeed go unfixed until if/when they can reproduce it (or somebody else with the issue assists them).
If anyone is experiencing this issue and is willing to help the devs, contact @avatar or @vasily_bagirov via private messages!