Shift+Arrow up/down broken

Hi, I’m having this bug every now and then but I can’t figure out a way to reproduce it.

For some reason when inside the MIDI editor, sometimes the shift+up/down note stops working as intended.
Instead, since I have two monitors, the second one displaying always the mixer, I can see the track selection moving to the next track, it’s like the MIDI editor window lost focus.
NOTE : I checked if the caps lock was activated by accident, and it’s not.

Any way to fix this ? Of course it goes away by restarting the app, but it’s still quite annoying when it happens.

Thank you