Please choose:
Follow the protocol exactly. This decision is above your role. Your job is to handle the customer, not reverse-engineer a product engineering call.
Tell her honestly what you have seen โ but keep it verbal, informal. Don't put anything in writing or escalate formally.
Handle this customer carefully, then raise your concerns with your manager before going any further up the chain.
Tell the customer the truth: "I'm not comfortable saying there's no fault. I've seen this pattern before. I'm going to log this formally and escalate it โ and I'll call you back." Then write the escalation memo that night.