XF 1.5 Changing styles causes issues with overlays

[Robust]

Changing to another style seems to cause issues with overlays and causes js to break.

I duplicated a style (exported it, and imported it). I changed nothing but the style's display name.

No pop-up or overlays work. They all trigger this error:

Uncaught TypeError: jQuery.easing[jQuery.easing.def] is not a function
    at Object.swing (xenforo.js:151)
    at init.run (jquery-1.11.0.min.js:4)
    at i (jquery-1.11.0.min.js:4)
    at Function.n.fx.timer (jquery-1.11.0.min.js:4)
    at lc (jquery-1.11.0.min.js:4)
    at HTMLDivElement.g (jquery-1.11.0.min.js:4)
    at Function.dequeue (jquery-1.11.0.min.js:3)
    at HTMLDivElement.<anonymous> (jquery-1.11.0.min.js:3)
    at Function.each (jquery-1.11.0.min.js:2)
    at e.fn.init.each (jquery-1.11.0.min.js:2)

 

[Mike]

This would likely point to some customization on that style interfering. If I had to guess, it'd be related to some custom JS being loaded.