It's still not obvious why this would be different for even vs. odd blade numbers or why changing one blade throws the others "off". If you have two blades and

It's still not obvious why this would be different for even vs. odd blade numbers or why changing one blade throws the others "off". If you have two blades and change one, you need to be concerned with the other blade. If you have three blades and change one, you need to be concerned with the other two blades.