Layout of Admin overlay is not correct

When I use Panelizer on an individual node (Full Content > Content > Click on the "wheely thingy" on the right of some field > Style > Change, the overlay appears. Then I go for Custom Style, and I can edit all sorts of font stuff etc. Works just fine.

However, the layout of that overlay has a few shortcomings.
1) Things "bleed" through the overlay limits - or, put differently, the borders of the overlay don't reach far enough down. This happens in my own theme as well as in a virgin Bartik, both used as admin themes. You can see this on two of the included pictures. The "Finish" button goes all the way down to "Powered by Drupal", and the slide rulers to the right of the overlay window also go beyond the bottom border of the overlay (or at least the white body pane of the overlay).
2) The "Close Window" link in the top right corner also looks a bit strange. This happens only in my own theme. In Bartik, it displays correctly. Since it happens in my own theme, I am probably to blame myself. :-). Just wanted to mention it, though.

Nothing major, but looks do matter :-)