Sorry to hear the frustrations you are having Greg. In situations like this, it is at this time I just down tool and walk away for the night. Sleep does help clear one's head. I've had the 775 motors seize up on me before but that was under heavy load on Kaizen.

The hubs are 6061 aluminium, which do warp somewhat, as is the grub screw I think. What I figured was that under shock, the ends of the grub screw warp a little, causing it to bind in the hub. I trialled smoothing off the end of the bolt about 5mm on Azriel but that doesn't seem to work. A high tensile steel cap head bolt might be better for handling the forces involved if it isn't one already.