C'mon - I know you can help me with my Bosch dishwasher?

Still waiting for help with my Bosch dishwasher - posted question aayges ago!

Lower propeller arm won't rotate during programme. Rotates freely by hand (with door open obviously). Top arm works. Cleaned dishwasher with HG specialist cleaner. Cleaned and de-scaled lower arm three times - made sure holes clear. Water comes thru propeller arm if you hold it under a running tap.

Help! What else can I try? Is it just the power of the water that turns the arm? I must be sooo close - don't leave me stranded to call in an engineer after all this! Please....