Megado - A shaft that should stay down, comes up when you make a shed

Possible reason: The dobby hook of the faulty shaft did not come high enough after the previous shed. The screw head should snap back above the blocking plate. Because the screw head stays against the blocking plate, the dobby hook remains extended forward and will be picked up by the knife, making next shed.

One reason why this happens is that the shaft does not go down to its lowest position because it sticks to a shaft bar of the neighboring shaft. Leave some heddles at the ends of all the shafts. This will help to guide the shafts along each other. Also be sure that the Texsolv cords run through the
slots of the shaft bars.   See the related article Megado harnesses are sticking