Last modified: 2014-06-26 22:13:08 UTC
Created attachment 14375 [details] screenshot of problem I opened the viewer and scrolled to the description bar up while the image was loading. The image loaded and positioned overlayed on top of the description bar. Then moving the position of the mouse caused the order of the layers to switch to what is expected.
Can you reproduce this issue on beta? http://en.wikipedia.beta.wmflabs.org/wiki/Lightbox_demo If not, then it's been fixed and will be deployed soon (if not already) to commons.
Assuming this was fixed, haven't seen anything like this for a long time.