Magic spell? The only spell I know is: 'Wingardium Leviosa'. It worked for Harry Potter but I'm not sure it's that great for stuck midi notes! Unfortunely, I cannot give you a definitive answer, but it's worth looking at the 'Midi-in meter' at the top, centre of the Edit screen. If you are not playing any notes, it should be blank. If however, a note on your keyboard is stuck, a midi-representation of the offending note will be showing (something like: 1 C3 49). Alternatively, if you press and let go of a key and the DAW/computer has only received the 'midi note on' command and not the 'midi note off' command as well, the note will also appear in the monitor and continue to play. I frequently have this problem, especially when I play a lot of notes quickly in succession. This may be due, in part, to the fact I use a slow, 2017 Macbook Air.