Oh, I know which one you mean! It is probably level 3 if I am not mistaken.
This is actually our fault, I think this one is easy to miss. You have to stand right below that suspicious block and just spam the jump button to gain enough momentum to glitch through the ceiling. The issue is that we changed the player sprite quite late and somehow it does not show the jump animation in that spot properly, so it looks as if you are just stuck and cannot jump in that spot. So I assume you probably tried this, but did not keep jumping because you thought it had no effect.
so yeah, that is actually a bug, not a feature.