Reymond Drill

For one, it's actually quite old, more than 7 years old I think. And also to clarify for Jokeyman123, pressing individual keys is fine but if I decide to press a key with another key, certain keys just don't make sound even if they did when I pressed them individually. Also, whenever I press any random key, it seems only a few certain keys don't work with it, but when I press another key, a different combination of keys don't work with it. For example, if I press a C note in one octave, A B C and E might not work with it, but if I press A, D E B and G might not work with that key

It has that problem regardless of the surface it is situated on

As the pretty long title says. On top of that, even some individual keys are not working either and that might just be a problem with the keys not making proper contact with the strip that lets the casio knows a note is being pressed maybe?? I'm completely not sure for the other problem though. Any help would be appreciated.