In the following JsFiddle, the second list isn't draggable in Firefox (and maybe other browsers). Works on Chrome though.
Moved example: http://jsbin.com/gebega/1/edit?js,output
Just for information, the same issue exists for Edge too.
Apparently adding option
forceFallback: true
makes it work for Edge and firefox.
But it breaks groups.
Most helpful comment
Just for information, the same issue exists for Edge too.
Apparently adding option
forceFallback: truemakes it work for Edge and firefox.