playReverse function not working properly

Hi to all,

I made a simple slideshow with a back button who uses the playReverse function. But when clicking this back button, the slideshow sometimes skips some slides. I used a sym.stop(); on every slide.

(I know there are a lot of other ways to create a slideshow, but I need this to work.)

The solutions should be quite simple, but I can't figure it out. I uploaded the (example) file;

https://app.box.com/s/2kp8hiatdffrgi5azzhv

Does anybody know a solution?

Thanks in advance