When a department stops performing at the desired level, ask what has changed. Have customer needs increased, do you have changing priorities, has the competition for your product or service increased, or is it another business impact? Customer needs have a way of increasing over time – the bar continues to rise as you meet existing needs. Priorities continually change as the business stabilizes or evolves. Products and services have to change to keep pace with the competition.
If you start a business process improvement effort by blaming the employees who support the process, the finger pointing can easily go both ways and nobody wins. Sure you may have a problem employee, so deal with him or her. Most employees, though, want to do a good job.
Involve employees who work in the process in the improvement effort and let them know you are not pointing your finger in their direction, but rather looking at how you can collectively improve the process to keep customers engaged and committed to your product/service line.