Wow, what a spectacular design blunder, but it was not the first! Some time in the 70s engineers got the brainwave that they could replace metal parts with nylon, and in some cases plastic! There was little experience with such a modification and the early ones resulted in a lot of failures. Reminds me of my mother's old Husqvarna sewing machine from around that same era. Hers was the first model on which they had replaced a lot of the moving metal parts and bearings with nylon and plastic ones. She only had it for a few months and it started playing up. As time went by it gradually fell to pieces. It was more times in the shop getting fixed than being used.
Engineering has improved since those times, but it seems they still haven't learnt their lesson. My self-propelled Supa-swift mower has been no good since Day One. They have a very weak plastic pully working with a solid metal one on the drive shaft. Of course it suffers from slipping and the friction causes heat which causes warping. I only get about three rounds of the lawn and without fail the belt falls off. Then I spend half an hour re-positioning the belt, only to have the same thing happen. The only good thing about it is the big Kohler engine. But it is so big that it is a very hard mower to push around without the belt drive. This mower has basically sat in the shed since I bought it and has had very little use. One day I will remove the Kohler engine and get rid of the geared wheels and belt drive. Put ordinary rear wheels on it and buy a much light 450e B&S engine. At least I may be able to use it, instead of keeping it as a shed ornament.
Just a thought, I wonder if an engineering place (or clever backyard engineer?) could make you up the same drive gear out of metal? A 3D printed gear drive sounds like a bad joke to me!
