Issue Overview

The Fix toolbar to Block option seems to work sometimes and not other times. You can see in this screenshot

and the one below, that the Fix toolbar to Block option isn't selected, yet the toolbar is fixed to the top of the block. If I select the Fix toolbar to Block option, the toolbar for other paragraph blocks actually stick to the top of the block. When I turn this option off, the toolbar moves back to the top of the screen for the paragraph blocks, but not for the other block at the top of the post (which btw, I have no idea what type of block it is!!).

Steps to Reproduce (for bugs)

1. Select and deselect the Fix toolbar to block option and notice that some toolbars move and other dont

Expected Behavior

I would expect that the toolbar on every block would switch between being displayed at the top of the block, or at the top of the page

Current Behavior

Behaviour is inconsistent. The toolbar moves for some block but not for others

Related Issues and/or PRs

#3708

Firefox Quantum 57.0
Gutenberg Version 1.8.1
macOS Sierra 10.12.1