I had the Title/Icon Font Size and Description Font size sliders disappear, too, so I bought the pro version.
I thought it was because I had added so many accordions to that particular section. I had already recreated another section that had 3 accordions and the sliders disappeared. The new accordion displays the sliders with 3 accordions. The second section (the one that prompted the upgrade) has 6 accordions. It made me think it was a size issue.
Here’s a screenshot:
https://dl.dropboxusercontent.com/u/11473902/responsive_accordion_no_sliders.png
