Hotpoint Aquarius WM22 (1000 De Luxe)?

I have a 12 year old version of the above washing machine and have noticed that recently the drum has become misaligned. It still turns, spins etc, just the whole assembly isn't mounted straight in the machine. The gap between the drum and door is much smaller on one side than it is in other. The concrete weights are in place, springs in place, and the dampers appear to be ok (although one is slightly softer than the other). Any suggestions as to what could be causing this!? Thanks!