If the Adblocker Add-On is installed on Firefox and you click into the dotted area of a component placeholder, the dialog that opens is not topped. Actually, it very shortly appears, then is put into the background. Note that clicking on the "Plus" icon in the bar of the same placeholder does not cause this effect - this seems to be related to how we've implemented the click inside the dotted area.

I'm usually disabling all add-ons when running user tests, but forgot Adblocker. Since it is a very common plug-in, I think we should have a look at this at least, although I don't consider it a top priority.