EDIT: Currently it leaves the context menu on the screen, due to a bug for Firefox-on-Windows with apparently no workarounds :-/ I'll file a bug report to Firefox.
You mentioned that it doesn't work on some pages like Facebook ... Can you try again after updating to the latest version of this extension which I have published just now.
If you are still facing the issue, kindly create an issue at https://github.com/webextensions/close-tab-by-double-right-click since it is easier to follow there :-)
