Un-sticking a Music-Time Keyboard 470 or Medeli MC-36

The next instrument in the pile I got from the flea market is this Music-Time Keyboard 470. I have recently discovered that it is sold under several brands and model names and the most common seems to be Medeli MC-36. I am pretty sure that it is the same electronics that are inside the Mr Platinum GC-6034 I showed some years ago - it has the same rhythm I used in this song    • "Vores damer" - on Mr Platinum GC-6034   There was a problem with this keyboard: Some of the buttons where rather sticky and one of them was stuck and could not be pressed - actually it was stuck in the pressed position, so I had to open up the instrument and un-stick it. The music is a variety of the build-in songs. To my great surprise none of them hit a copyright match, which most of my videos do - maybe I am a better musician than whoever programmed this thing............ nah, probably just coincidence.