/folder_contents: can't click on actions

I have a problem with (several) Plone 5.1 sites when trying to click on the 'actions'.

When clicking on the actions (the pointer changes to a hand), I still get the 'move' action.

I notice there is a javascript error:

TypeError: window[b.options.drop] is not a function. (In 'window[b.options.drop](f,f.index()-d)', 'window[b.options.drop]' is undefined)

in logged-in.js

UPDATE; I installed a new, Plone 5.1c2 site, and the js error is gone, but the problem remains

This happens in my theme, but also in barceloneta them.

Any suggestions ?


Looks like there is a CSS problem, something like:

.actionmenu-container, .btn-group actionmenu { z-index: 99 }

(or probably a lower number than 99) solves this

Actually, it does not really solve it, as the action icons has wrong z-index (but I can not figure out from where).