HummingBird breaking my site

I have tried so hard to so hummingbird - it is THE reason i got a WPMUDev account in the first place. I REALLY want it to work, but whenever I use it to breaks my site, and I have to deactivate it again.

I start with only minifying certain files and and making small changes to see what works best - cause I know all sites are different - but I don't know how someone can work with this plugin at all.

Right now, i've disable the plugin again, but it's effects are still on the site, cleared the cache ... but it's still there.

What should I do?