I would like to encourage you to report your bugs with the smiley at the top right corner.
A few days ago I upgraded my LAB vCenter to 6.5. With this release you get the new HTML5 Client. There are some improvements especially in responsiveness. But there are also a lot of bugs :-/
So don’t worry that your feedback wouldn’t be heared!
For the interested people, here is the fling that is behind the HTML5 Client.