Dear OP, My organization had received a notice in 2018, almost similar to the one you have received, and we made a point by point reply with proofs attached.
Two cardinal mistakes must be avoided in making the reply
(i) Do not make a wishy-washy reply
(ii) Do not make the reply without actually liquidating the observations, the inspectors can return to check implementation once they receive your reply.
The reply that I had made to the notice we received is attached (company info has been redacted) for whatever it is worth.
Regards
Arun