I have exactly the same problem. I have always had this problem since purchasing the machine but at the start it was just now and then, now (2 years later) it is everytime I put on a wash. I haven't tried banging on the top as the machine is quite tightly housed. This problem is annoying as it can take a while to put the washing on! Such a shame as everything else is fine with the machine! Wonder if the problem can be remidied and how much it would cost!
S Thornton, August 2011