Can the patentee ask the prior user to stop production?

Of course. Paragraph 2 of Article 69 of the Patent Law stipulates: "Those who have manufactured the same product, used the same method or made necessary preparations for manufacture and use before the patent application date, and continue to manufacture and use it only within the original scope; The "original scope" here refers to the same product that your factory has manufactured before the date of patent application, or the preparatory work necessary for manufacturing and using the same method.