Reluctance to Provide a Paid Sample
A factory unwilling to provide a sample before a large deposit, or that pressures you to skip sampling entirely, is one of the most consistent predictors of downstream quality issues.
Vague Answers on Certification and Capacity
Evasive or inconsistent answers about certification status, factory capacity or production location (versus a trading company presenting itself as a factory) are worth treating as a serious caution flag, not a minor communication gap.