The water from the hose I was using to fill my birdbath suddenly stopped flowing. I turned to discover that it had gotten a kink in the hose. A perfectly good hose with one kink stopped everything.
The same is true with your staff: one kink (i.e. a troublesome employee) can halt the efforts of your entire team. As a supervisor, you may be tempted to overlook this temporary disruption and justify in your mind that it isn’t always that way, that sometimes the process flows smoothly, but unless you tend to the issue swiftly, everything else will slow to a trickle.