For reproduction... I think it was the "spread excavators out" function (which is very useful for several other mining scenarios, as it makes excavators far less prone to digging narrow, collapsible channels on concave, multi-excavator mines, or other mines where they're digging towards the tower) that had it travel to the far side of the mountaintop being trimmed, to a point that I guess it could navigate, and promptly destroy its own path. The other cut would have been the other three excavators in the mine, after it made the unwise trip.

At the end of the day, this is what that "recover" button is for, isn't it?

Update 4.1 | v0.8.4b (b593)