jm-slide-buttons layer problem

I have a problem with the slideshow buttons showing through my mega menu. My mega menu has a z-index of 900 and the buttons have a z-index of 101, but the buttons still show through.

I have hunted, looking for where the z-index may be wrong but can’t find it. I have attached a screen print of the page, as the site is not viewable by the public yet, and is protected.

If you need access send me a private message with your IP and then you can view the site.

Is there someplace where javascript is overwriting the z-index? Or what else am I missing?

Thanks
Janice