On Legend Difficulty (Not sure if this is what causes it), on any stage, if you are full to the top, and the timer for a drop runs out and you are on a spot where the drop can't happen, the game will rapid fire try to drop the orb over and over, making the "can't drop" sound effect rapid fire and the timer bar to underflow, and it starts filling up again, probably 'cuz going into a negative value.
This also causes the 10 second timer to go down super quickly.