If the patent examiner's fault leads to the rejection of the patent, then the reexamination fee will have to be paid. Shouldn't this loss be borne by the filing date?

This is a rule and ordinary people cannot change it.

For invention patent applications, the reexamination fee is 1,000, which can be reduced to 400 if the company's fee reduction conditions are met, and to 200 if it meets the personal fee reduction conditions.

For utility model or design patent applications, the reexamination fee is 300, which can be reduced to 120 if the company's fee reduction conditions are met, and to 60 if it meets the personal fee reduction conditions.

If you entrust a patent agency, additional agency fees will be required.

Submitting a reexamination document is similar to providing an ordinary opinion reply document. You can make modifications and statement of opinions on the rejection decision to prove that your patent application meets the authorization requirements. Documents are submitted to the Patent Reexamination Board.