I set up on my Mac a behaviour similar to one I like on PC: a shortcut to move a window to the right or left of screen. It is equivalent to the "Move Window to Left Side on Screen" that can be accessed through hover on the green window button (but much more practical and quicker).
But with Firefox it does not work: the window does go to the side of the screen… then instantly comes back center.
Painful and a reason to change browser for me 😕
Does the window stay where you moved it if you use the mouse method (only the keyboard shortcut method fails)? Or does it fail either way?
Can confirm that the issue is only when you use the keyboard shortcut. Using mouse method on the green window button or from the Window menu works fine.
Using a shortcut moves the window to the side and then to Zoom. Very inconvenient.