Not opening in primary display

[MTaggart97]

I have two displays, the built-in display of my laptop and an external one. The external monitor is set to the primary display, however, when opening the app it will always open in the built-in display. As well as this, opening files while the window is in the primary display will open a window in the built-in display.

I think the expected behaviour would be for the app to open in the primary display and for subsequent windows to open in the same display as the main window.