I think it is obvious, as it appears does Iron Duck, that the Continental mechanic did not exercise his duty of care to perform the repair according to applicable procedure.
He couldn't exercise his duty of care
because he had no duty of care. The duty of care did not lie with the natural born person (the employee) but with the legal person (Continental). The company controlled the terms and conditions of his employment, they directed his activities, they hired him, etc.
That's why this ruling against the employee doesn't pass the smell test. It's 100% bunk. If the ruling is in accordance with French law and French case law then that law is bunk.