Thumbnail editor stopped working on slider

I am using simple Catch and come across a big problem with the slider. I have been using the Thumbnail editor plug in and it has been working fine, the images were cropped in and fit in the slider. And then inexplicably the slider changed all the images seemed to reset themselves suddenly there's white lines on either side of the images. I've tried to recrop hem on thumbnail editor and it wont work. I've even tried other thumbnail editors but the same problem. Any ideas how i fix this?