Column WIP limits…
… bring about the moving constraint syndrome. Chasing the breaking WIP limits becomes a “Whac-a-Mole Hysteric Hysteresis” game.
When “constraints” (that is, bottlenecks) are constantly moving in the system, it is a sure sign that the real constraint is not known; and above all, the real constraint is not managed.
Learn to identify and manage the real constraint.
Quoted from: Tame the Flow.