I've been a long-time user of MB2 (both free and premium). When I first heard about MB3 I was excited by the idea of having one centralized security solution from the makers of the excellent MB2. That excitement disappeared rapidly. I'm sorry to have to say this, but MB3 is a buggy mess that should be labeled as prerelease/beta software. I'm sure there will be questions to post my setup and try to troubleshoot the exact issue but I know my way around computers and this software is labeled as release. It should not have this many issues, let alone slow a maxed out Surface Book to a crawl. I have browsed these forums, used every version from 3.0 up to 3.06, I have been tracking the changelogs, ... I am clearly not alone, but yet there seems to be very little to no effort by Malwarebytes to communicate clearly about the multitude of issues. Just now, to uninstall the app, I had to manually kill one of the MB services that caused the uninstaller to hang.
I'm out for now, unfortunately that means I'm losing time on my subscription but I just don't have the time to troubleshoot anymore. I sincerely hope you'll be able to get this product in a more stable state soon but it is clear it won't happen overnight.