How to raise it with the supplier
The notification is where most claims are won or lost, and the difference is almost always tone and completeness. Write it once, in writing, with the facts and the evidence attached, and state what you require and by when. Then allow a reasonable period for a substantive response before escalating.
Structure the message in four parts. First, the identification: order reference, supplier order number, delivery date and the affected specification line. Second, the facts: what was inspected, how much of it, in what state, and what was found, with counts and measurements. Third, the assessment: the severity class, why the deviation is a deviation, and the quantity affected expressed as a count and a proportion. Fourth, the request: what you want, by when, and what you are doing in the meantime.
Keep it factual and unadorned. Do not speculate about cause, do not assign fault and do not include an account of how inconvenient this is. Supplier responses to narrative get slower and less useful, because the supplier has to respond to the narrative instead of to the problem. One paragraph of context is useful; a page of grievance is not.
State the disposition of the goods in the meantime. Say explicitly that you are holding the affected units, that you are not using them, and what you are doing with the sound units. Holding is the neutral position: it preserves the claim without making any admission about the rest.
Do not withhold everything on the first message. A wholesale hold across an otherwise sound consignment is a negotiating tactic rather than a defect report, and it invites the supplier to treat the entire order as disputed. Reserve the full hold for the situation where you genuinely cannot identify which units are affected.
Escalate on a defined ladder and give notice of it. Claims contact, then account manager, then the person who signed off production, then commercial escalation. Tell the supplier you are moving up the ladder and why. Most claims resolve before the second step, because the second step usually involves somebody who can approve a decision.
Close the loop in writing. Whatever the outcome, record the agreement, the quantity and the date, and note what has changed in the production process as a result. That last sentence is the one that protects the next order.