The latest release of Chrome that has been rolling out this week has been causing a bunch of issues related to flexbox, including the Eureka browser in Redactor 2.
While this looks to be resolved in the Chrome 50 beta channel, we’re not sure when that will be available so we’ve worked around this issue in Redactor 2.0.7 to make sure Eureka looks and works as expected. The Redactor update is now available.