Comment 1 for bug 106351

Thank you for your report

That happens because if you right click on the bottom right corner of the page area the menu does open just where it only fits and then the option of the menu that gets instantly marked is the last one "Switch Page Direction", hence that behavior.

I agree that it's a weird behavior and that the menu should be placed somewhere else when the pointer is at the right bottom corner. I'll mark as wishlist