Hi it could be what you said if you heard possible ruble fall that would prevent the sash weight going up fully ,so stopping the sash to fully close if you press sash down does it try to close on one side only ?can you pull on the cords to try to close. if you are not able to, then I'm afraid it could be a major strip down, to remove jammed in objects out of the weight boxes,you may get results by removing the pulley wheel and prod through the opening to dislodge any debris hth Tez