you are not the first to write that off as a bug there is even a hint that appears 10 s after you get near that acid "You : I bet even the acid is fake" so jupming in a aria near that acid (that's fake) turns off your gravity and is why you get stuck . so totaly intentional you are suppose to get back to the previous check point (if you stuck) vie ESC menu or Z death and go again without jumping just go straight thru the acid won't kill you :)