Bosch Axxis Washer Front Loader - Drum won't turn

The drum and motor move freely when turning by hand, and you can hear a relay click when it's time to either wash or spin, however nothing happens. The problem is somewhat intermittent - it has worked a couple of times after it "stopped".

There is some sort of vacuum control (brown disk) mounted on the upper right hand side inside the machine. It has three screw adjustable controls. Could this part be faulty?

Thanks in advance

Thure Meyer