Part Selection Issue

I’ve had an issue for sometime. When selecting parts there’s a very strange behaviour.
If I click on full score (to drop down the parts) either nothing happens or the parts list pops up and disappears within a fraction of a second.
The only way I can then access the parts list is, with the pointer over ‘full score’ wait a second or so and move it left of right. Then the parts list drops down.
On some occasions using the down arrow makes the list appear.
I have tried to screen record this and every time I do it behaves as expected. Turn screen recording off and the problem comes back. This pattern repeats.
Done all the obvious, restart, reboot, no other apps running etc.

MacBook Pro M2, 16gb, Sonama 14.6.1

Thanks
Paul

Is this on an external display, or the built-in screen?

One thing that might avoid having to use that menu: if you press W, it will switch between the full score and the part layout of the selected note.

It’s the built in screen

There’s a shortcut that has passed me by. Thank you