On the History page in the mod tools, the SE multicollider doesn't drop down, instead it purely acts as a button to the http://stackexchange.com address.
Takes us to this:
It does work perfectly fine* on the other pages, and the issue is not present on Meta Arqade:
* This does occasionally happen on other (not mod-specific) pages when the page does not load fully before clicking the supercollider, however on the History page this is occurring all the time - even when the page has completely finished loading.
It is occurring in the latest versions of Firefox/Chrome that I've tested and Chrome on Android that Ash has tested.