Some dialogs position outside browser window

Some dialogs position outside browser window

The following menu items grey out the current page and put up dialogs outside the bounds of the current window. This gives the appearance of the browser being dead.
  • Page options menu
    • Copy to
    • Add subpage
  • Hamburger menu
    • Support
Observed in Firefox latest on Windows. Using a multimonitor system. Works fine on center monitor, but when the browser is on the left or right monitor the problem occurs. Apparently the dialogs are positioning relative to desktop, but can't be seen when they are outside the browser window area, unless user scrolls.

My bug-tracking Id: GWZ1006