Upgrading to v3 ACF blocks semi-fixed it for me too, you now get the preview looking ok, and you can click the edit icon to pull out the sidebar so it is bigger.
I still hate it though, I don’t want to preview my blocks, this is a backend editor, I want clean inputs so I can put in the data. This is trying to be a frontend editor, which I do not want!
Yep – broken here too. Only solution at the moment is to roll back core.
It’s the bit with a class of “media-frame-menu” if that helps.
Does anyone know if this is possible please?