It sounds as if you have a sock or similar between the inner (rotating) drum and the outer container.
If you rotate the drum by hand your may be able to feel a lumpiness or intermittent drum sticking. If there is then you may have to remove the heater element to get a wire hook on the sock to pull it out. If you have never replaced or re-fitted an element before it may be best to get an engineer to do it for you. It the job goes wrong you could end up with a huge flood!
Not a job for the inexperienced guy.
OJ
August 2011