How Can Multiple Die Clashes Happen ?

First, might I congratulate other contributors who've managed to show pictures of coins exhibiting die clashes - I can't match that for the subject of my query - the marks simply don't photograph well.
I have observed clash marks on a large number of the coins of Queen Victoria (third farthings to sovereigns). In several cases, parts of the obverse design appear multiple times on the reverse (usually slightly rotated, sometimes moved slightly sideways). I can't see how this can happen - if the dies remain fixed in the press, the clash should always strike in exactly the same place.
Can anyone enlighten me ?

Just to prove that I know what a clash is, here is a photo demonstrating a single die clash (on the reverse only) on a British 3d - note the upside-down face to the left of the "3".