Seems to be a limit on the number of Leader Foregrounds you can have in the subdirectory.
As shown in the quick video below it only loads about half of my FGs. If I delete one of the previous images, I then get the next image, so not the next image, but rather a hard count of what can load.
http://miniworld.com/galacticCiv/GCIII-C-LeaderFG-Load.mp4