I drilled two holes through the plastic piece and metal shaft of the bosh. Then I pushed some Ikea stuff in it to fix it. I don’t know how the pieces are called, but you can find a picture over here.
I think you could also fix it with small screws, but take care you don’t split the plastic piece in two. Additionally, the screws may not be too long because then it will block the inner space in the shaft. A possible downside to screws: they may become loose due to vibration, and then you have some metal stuff inside a running machine… If the Ikea stuff comes loose, it’s just tiny pieces of plastic 
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Experience: first I only drilled one hole and used 1 Ikea thing. It wore off after about 10 hours of drilling. Then I fixed it with two holes/two Ikea things. I’m running the machine for many hours and it still holds. I suspect, in time I will have to replace them, but so be it.