Media Gallery description not displayed on full page in Chrome and Safari (MAC) [#1932310]

I want to display the description via "show media on full page" but it only can be seen in firefox and opera... chrome and safari seems to move the whole div beneath the image because the whole theme ist stretched in length through a lot of attached white space under the gallery image.
i use a subtheme of the base theme boron.

i've tried...
... using lightbox with displayed title & description > this works.
... checking the css/html code via chromes developer tools > it pointed out that there exists an

which is "overflow:hidden" in media_gallery.css... if i change this via chromes developer tools to "overflow:left" > the description can be seen, but if i change the code in media_gallery.css the whole gallery gets demolished...

does anyone know how to handle this?

thx so much!