People are often frustrated when required to use a cause & effect diagram to find the root causes of problems. The diagram puts too many possible causes on the agenda simultaneously that it creates cognitive overload no wonder people often use a guessing/voting process to identify the most likely cause (which in itself isn’t logical).
Preliminary risk assessment (e.g., Likelihood X Impact) and the results of previous audits (e.g., number of NCs) are often used to help prioritize the audit schedule.