Yes you need a disclaimer or terms and conditions clause specific to your field and have your client agree in writing.
Here in Europe email is a legally valid form of writing.
If your client’s business is a legal entity and legally owns the implementation, they are responsible no matter who did the engineering.
Of course you want to keep a high reputation so it is good going a bit in-depth about the things you are building and have your drawings double-checked. But again the final responsibility is with the legal entity owning the product and with certain business structures, natural persons can never be held responsible unless grave misjudgments were made.