Hello, signing in with the same issue. Yesterday the buggy menu auto-clicked on "Stack Tabs by Hosts" and I was in a panic. Fortunately, I had already enabled session backups, otherwise I might have switched to some other browser...
For me it happens even without menu scrollbar, regardless of "User Interface Density" (just switched to Compact, didn't know that option existed; since I had two monitors with very different sizes and resolutions, the regular was taking almost the whole height of a screen). In some places on the screen it seems to happen more. It looks to me like some rounding problem?
https://imgur.com/a/HTN9djK
In the video, every time a menu item is highlighted (lighter gray), had I not kept pressing the button, it would have clicked on the menu item automatically.
i3wm, 7.1.3570.42