Each Viewport window can be assigned a Local Camera to view through when Num0 is pressed.
However, if a camera is set to be the primary camera by pressing Ctrl-Numpad 0, all the Local Cameras in every viewport are set to that one as well. This is very frustrating since the only reason you would specify a Local Camera in the first place is because you DON’T want to see it in those viewports.
What’s worse is that since it’s a UI setting, undoing the command still keeps the new Local Camera settings in these viewports, forcing me to go through and reset them all again manually.
Pressing Ctrl-Numpad0 shouldn’t affect the Local Camera setting at all.
Before:
After: