Legal Question in Business Law in California

It sounds legal. You don't describe any crime. But that doesn't really seem to be your issue.

What you really seem to be asking is if the supplier has adequately itself from any and all liability for the parts. Unfortunately you have not provided nearly enough information to even begin to render an opinion on that question. You need to retain an attorney to go over all the facts and terms of the purchase and sale transactions, including any documentation. Then you probably should pay for another few hours of attorney time to go over and restructure your business practices and documents to make sure you don't face this kind of question again in the future with other parts.

The Uniform Commercial Code and related international laws generally present two or three hurdles for the supplier to meet. First, the buyer generally has the right, and the duty, to make an inspection of the goods upon arrival, to make sure they are the right merchandise, that there has been no damage in transit, the quantity is correct, and there are no obvious defects. This usually completes the purchase transaction - the goods are sold, title passes, payment is due, and the buyer can use or resell the goods.

However, the seller's responsibility doesn't end there. In most transactions, unless the contract provides otherwise, there is an implied warranty. In addition, in many transactions and in many industries, including the electronics industry, sales of goods carry express warranties that are either spelled out at length in the contract or adopted by reference to an industry standard. I've forgotten the industry standard in electronics - something like EIA or EMA - but you being in the trade may know of it.

Components which later on fail to meet either an implied warranty of fitness and suitability, or an express warranty, will probably result in future warranty claims from the dissatisfied buyer even if they passen an initial inspection and test. It's like having a contractor install a 30-year roof. Being watertight the first rainy season does not answer all the questions.