Step-by-step explanation:
When a problem is discovered in the system design or manufacturing process, it generally gets reported to all concerned (if the company has an appropriate culture). Depending on the nature of the problem, a "quick fix" may be found by the discoverer, or by someone to whom the discovery is reported. In some situations, what seems a simple problem requires a rethinking of the entire manufacturing process, possible product recalls, possible plant retrofits, and even larger ramifications. This can happen regardless of where along the line the problem is discovered.
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Hypothetical example:
A test technician determines that a lithium battery charger sometimes gets confused and doesn't shut down properly--continuing to charge the battery when it should not. If the proximate cause is a wire harness routing or a component improperly installed, a manufacturing engineer may be called in to address the issue. The manufacturing engineer's investigation may determine that a number of battery chargers have been delivered with the problem. Further investigation may reveal a potential for fire in situations where injury or loss of life are possible outcomes.
Assessment of the design by manufacturing, process, and design engineers may reveal more than one potential cause of the shutdown/fire-hazard issue, and that the location and nature of any fire may release toxins or cause damage to systems and equipment beyond those in the immediate vicinity of the defective battery and/or charger.
Such ramifications may require the attention of one or more systems engineers and/or a rethinking of system failure modes and effects, including fire detection and suppression, throughout the product. The product may be effectively "grounded" (taken out of service), with possible customer revenue implications, until such time as the issues can be satisfactorily resolved.
(Note: 787 Dreamliner battery problems were caused by the physics of the battery construction, not the charger. The rest of the scenario above is not a bad match.)