OMG after (only luckily!) 2 hours of bitching around with Opera resetting and reinstalling stuff I finally found it was because of this. So yeah big fatty problems. I could only load pages in a new tab after restarting the browser for like 10 sec or so and then nothing would work anymore inside that new tab or any other tab, not even going to settings and opera://flags or the extensions. I even deinstalled all extensions and then tried reinstalling them but they wouldnt install back anymore.
Firefox on the other hand seems to be working fine tho, apart from one crash which I haven't experienced before in a very long time. But that may either be due to that I tried to close it too quickly after opening it, but yes it could very well be because of MBAE. I didn't try Chrome yet, so can't confirm that.
Win 10 - 1709, 16299.551