I did go through FedEx and they are the ones who sent me the notice of the reclassification and additional fees due.
Again, Disclaimer: I am NOT a lawyer!
Personally I would dispute this with the broker and CPB because:
The original shipper and their brokers are who determined which Harmonized Shipping Code to use. We end purchasers have no input on that so how is their screw-up our responsibility?.
Going back to at least 2014, U.S. CBP has accepted import of miners using those codes which of course reinforced shippers and their brokers continued use of those codes.
For large customers, if there were Federal actions underway to re-classify miners, did the brokers at least inform said customers of possible additional fees being levied?
Again, to me I feel the end purchasers should not be liable in any way as this seems to be strictly between the shippers/brokers and CBP. One or all of them screwed up and they are the ones that should pay what's due or ideally the CBP should just eat the previous losses and simply state that starting on such-and-such date all incoming miners fall under the new classifications.
Final customers should be held harmless for this kerfuffle as we had zero input to what happened.