Hi Pine. I don't think I'll ever know for sure. I am a murphy so anything is possible. I did put it together the 2nd time exactly as I did the first time - the difference was I replaced all parts the 2nd time. My suspicion is the hard black plastic housing was defective and allowed the silver cup to shift somehow... I also read somewhere that the impeller is flexible enough to correct itself if turned the wrong way initially. Like I said, I'll never know for sure as it worked fine for awhile and then it didn't.... Can't wait for the weather to moderate so I can get some hours on her. The only thing I've done since the last update is I installed a 2 bank battery charger/maintainer that will take the guess work out of battery charging. cheers!