I think I may have finally been able to reproduce this issue. For me, if there is nothing on the second screen, only a portion of menus will appear. I will try get a regression range.
Bug 1623018 Comment 8 Edit History
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I think I may have finally been able to reproduce this issue. For me, if there is nothing on the second screen, only a portion of menus will appear. I will try get a regression range. I can reproduce this on 10.14. It appears that the bounds of the update area is inconsistent on the second screen.