the seller will send me a new replacement board for the faulty one, so I hope that will fix it.
You are lucky, the seller seems to be honest, most sellers will just tell you "the miner was working great when we shipped it", hopefully, they will send you a working dashboard, although I'd prefer if you got a 1/3 refund instead, but still, a lot better than nothing.
where are you located? the bad hashboard could likely be fixed, and since it's reporting 64 Asics out of 65 it means likely that the 63-64th chip is bad due to bad connectivity, here are two things to try
1- Locate those two chips, you can do see by reading this >
https://www.zeusbtc.com/articles/information/182-antminer-s17-manual-download, apply some serious pressure on both for a while and then test the hashboard.
2- Put the hashboard in a plastic bag then seal it, put it in the freezer for 24-48 hours and then test it.