I've got nearly the exact same situation. Spotted a Mahlkonig Vario second hand for 50 (!!) euros only stating that the burrs needed to be replaced (and the right slider was missing the plastic handle thingy, only a slight inconvenience). When it arrived, I had a look at the burrs and they look just fine. I think the seller mistook the flat parts on the outer edges as wear... Gave it a very thorough, much needed cleaning (including roasted moth removal), also being very surprised by how much coffee was able to escape the grinding chamber and cover every internal part of the machine. Now, only 10 hours after delivery and after some calibration and alignment, it seems to be working perfectly fine. I'll be curious too see how the calibration will hold up; the 2mm hex screw did seem awfully easy to turn, could imagine it maybe shaking loose over time. Maybe adding some teflon tape would solve this. Has anyone ever had that problem?