My two button sets are working perfectly. On fields I select “Very Simple” as my set, I only see Bold, Italic, and Underline. On fields set to “Table Set” I see Bold, Italic, Underline, and a custom button I’ve created to generate a shortcode snippet.
The problem arises when I view the editor in IE or Firefox.
In Firefox, if you position your cursor inside any bit of text, and use the up and down arrow keys to navigate around, when you get to the top or bottom of the element, the cursor jumps to the beginning of the first element. So if I put my cursor at the beginning of the first paragraph, and pushed the down arrow twice, the cursor moves to the top of the first paragraph.
In IE (9, 10, and 11), if I click on any element, I get resize handles. I must click a second time on the selected element to edit its content (see screenshot below)
When I disable all plugins installed (including ACF), and leave the function above, this problem still continues. When I leave all plugins disabled, and comment out the function above, everything goes back to normal.