No problem, it sounds like the only problem is a too tight fitting drive unit. I can send another. I think you will find that your drive unit (prop assembly) doesn't easily slide off the shaft, there is probably a lot of drag. It has to be able to slide off the shaft to reverse, it reverses by flying out when it spins backwards. I can explain why you have this problem and it is our fault and we will fix it. The first pumps tended to hum and rattle, some of the drive units were too loose. Like every other drive magnet these are made in China, you can imagine it takes weeks to get new magnets from China to Germany by sea. As an interim solution we tempered the plastic, plastic is compressed when it is molded so if you gently heat it for a long period of time it "relaxes". These were then drilled to the correct spec but such a process is not perfect. The new ones just arrived at the factory about 3 weeks ago. In some cases the fit of these older ones was too tight, often they work themselves out with a few days of wear in. No matter, I can send a new drive unit to you if you just PM me the address to send it to. I just wanted you to understand how this happened and we have already resolved it.
