Sorry, I didn't know if I should say it or not.
The bug occurs with the "safe blocks" and with the initial block (the one that the player always appears at the beginning). You just have to stand on top of one of those two, and wait for them to reach the highest point where they disappear. When they do, the player will enter the state of "falling" but with the difference that you will be able to make infinite jumps, until you touch a surface again.
My theory is that it is not declared that the player is no longer on a surface when the block on which he is disappears in this way.