I am having problems changing the full screen slider images

I am having problems changing the full screen slider images on the fixer theme...

I delete the pixelated images - and then the "Add More" slide images button dissapears - so I can't add any images.

I tried to add images while the original ones where still there and this seemed to work.
But, then when I deleted the pixelated images, it also deleted my new uploaded images and the slider is left blank..

I can't see how else to access the slider than from within upfront - is that right and is this a known bug? Using windows 7 and chrome browser.

If I can help any further, let me know.
John