Quick update..!

Yes, it definitely appears to happen when I place the PNG over the slideshow. I have another instanceof the same image on that page, and upon sliding it up to cover the menu bar and the slideshow, the top half renders as a JPG while the bottom half retains its transparent background! See attached image.

Click image for larger version.  Name: Ashampoo_Snap_2015.12.10_08h15m14s_001_.jpg  Views: 146  Size: 22.5 KB  ID: 111145