Megado - One shaft sticks 10 mm (about 1/2") above the other shafts while it is in its rest position.

Question: 

One shaft sticks 10 mm (about 1/2") above the other shafts while it is in its lowest position.

Probable reason:

• One of the shaft bar clamps has loosened on one or both sides, and by accident, it was tightened at the wrong height.  
• Another possibility is that the shaft has become hung up on its neighbour - most likely because there are too many bunched up heddles on adjacent harnesses. See article Megado harnesses are sticking