The context menu can't be opened from the load bars. This is particularly a problem when the text label for the monitor isn't shown, since then only a tiny portion of the monitor is right-clickable and most users will not guess.
I'm using version 1.2.0.
git commit 23ec87473efc5dd9da19c1b1968915521d56b2eb
i reproduced by switching the progress bars on/off, fixed by introducing an eventbox around the progress bars, that eventbox is hidden/shown instead of the bars themselves (the bars lost their signal after being hidden)