I tried it again just after I posted back, and there are three distinctly different sounds. First one is the lock. Second one is the deadlock, and the third and subsequent ones is the re-deadlock. So second and third does sound different. But third, fourth, fifth etc are all the same. Anyway, like you say, it's obviously just trying to deadlock again, but the noise is different where the locking mechanism grinder shears a bit more off of the locking roads etc! :lol: