How to add thick borders to all slides on Impress handouts?

I’m looking to replicate an MS Powerpoint appearance where each slide has the same border (or drop shadow? I don’t know what it’s called). Here’s a good example of what I want them to look like: Pantheon | No Site Detected

I’ve added transparent rectangles with a 1.7pt-wide border to the preview page on top of the slide outlines, but the top-left slide doesn’t have a consistent border when printed. The left side of that slide always comes out thinner, at about .8pt. For what it’s worth, the print preview (but not the actual editor) also shows this ugly inconsistency.

This was all on two installations of Libreoffice Impress, one on Windows 10 and the other on Fedora 22. I’m using EN_US variants of everything.

Any ideas? Is this a bug?