I sent our Lawnbott out earlier this week (yes, in January… the grass was getting unusually tall and green in January and there were some leaves that had blown in that I wanted to mulch). Yesterday I got a phone call from one of our neighbors “I was outside and heard your mower making an unusual noise”. It turns out that he had hit something (I still don’t know what) and had one tip of the blade snapped right off just like the ones in your photo. The break caused his blade to go out of balance (thus the unusual noise the neighbors heard) and the vibration was enough to back out one of the blade screws completely. It looks like something similar happened with a blade screw in the picture you posted as well. I’ve walked the yard and haven’t found what he hit or where the missing blade piece is at.