Use this one-page root-cause worksheet every time a quality failure crosses your desk:
Problem statement: describe the defect, quantity, customer and deadline impact in one paragraph.
Evidence collected: attach photos, measurements, machine settings, batch numbers and witness names.
5 Why chain: ask why at least five times, and stop only when the answer points to a process or system gap.
Containment: list what is done now to protect the customer, who owns it and by when.
Corrective action: change the process, standard or training so the failure cannot repeat.