Kevin
My suggestion:
1. Never assume things can be fully resolved just by holding a meeting and getting commitment without follow-up checking … you will find that there are million and one excuses why the commitment cannot be fulfilled. Follow-through is the only way.
2. By the vast number of similar reported cases, there is evidence that this is a product quality problem (unless JZ can prove / demonstrate otherwise). JZ is contractually liable to replace and provide good quality merchandisable quality thus they shall be liable for all replacement + extended warranty period after replacement. Replacement of damaged units is the minimum … whether or not we need them to replace those units not yet exhibiting any sign of failure (at this moment) would be a decision that you / Ops should make.
3. Never rely on JZ alone … please also investigate / identify alternative source of procurement the replacement parts, check the lead time etc in case JZ fails to take further action.
Simon