For some reason, the "update issue" form uses a completely different, more horizontal layout than the "report issue" form.
As a consequence, if you have very long version names or issue categories, the "update issue" form can easily be wider than your browser window, causing some important fields like "Reproducibility" to be hidden completely.
The fact that the horizontal scrollbar is hidden at the very end of the form (which is typically not visible unless you maybe use your screen in portrait mode ;) makes the usability even worse.