Random uploaded headers not displaying

I have uploaded several of my own headers and have selected the randome option from within the ‘headers’ section within ‘appearance’.

However on the site all I get is the site title with no image displayed. When I select a specific header then this displays perfectly, but it seems the random option doesn’t work for me.

I am using the ‘retina’ theme – http://wpaisle.com/retina/

http://wordpress.org/extend/plugins/wp-display-header/