I nailed this bug and found simple workaround. Height of pp_content is calculated in function _getDimensions by copying hidden pp_details element offscreen and measuring its dimensions. This copy contains unstyled pp_close button (its dimensions are unspecified because theme style not yet applied). To fix this simply add this oneliner to your stylesheet (pixel size is valid at least for light_rounded theme):
I'm having the same problem and unfortunately that didn't work for me.
I increased the size of the description text, and for some reason 3 lines works fine on the 1st and 2nd slide of my show, but by the 4th it starts clipping. The images are all exactly the same size, so I have no idea what's going on.
I've tweaked the CSS by adding extra padding/margin to the bottom of some elements, but what ends up happening is the 1st screen (with only 1 line of text) has a big empty space at the bottom, and the last gets clipped.