In addition, not all suppliers are fixed from the beginning of the project, which leads to the recurring need for design changes. Procurement of some parts may take a long time. As a stopgap measure, engineers used estimated data to meet the requirements of the first few harness freeze dates. After a supplier procurement is complete, the actual requirements often do not match the engineer’s assumptions, and a change order is required to get the part to work properly. In some cases, suppliers were unable to meet the schedule and even decided to terminate their participation. This means that parts must be repurchased. New parts rarely match the electrical specifications of the original parts exactly. This in turn leads to more change requests to modify the harness.