I occasionally build electric hub motor wheels. The 12 mm axles with 10mm axle flats have a very annoying habit of trying to climb out of the V slots making the truing process a pain.
My fix was to modify a set of old style adapters that were designed to accommodate 29er wheels with tires in a TS2.
I cut slots to accommodate the 10mm flats and now I can spin the wheel both ways and the axle stays firmly seated.