Okay, I've written some code so that the disco person will fall down. You can find it on the following link:
The Disco game fixed to fall correctly and a picture of the new code
Let me know if you have any questions about why. I basically broke up the falling and the jumping into two different code blocks. One makes the person jump, and the other makes the person fall "if not touching <any of the other sprites>". see the picture and try it out in the ".sb" project.