I'm only using primary m.2 and gpu slot nothing else, and no it should not share bandwidth with Lan in any way like that unless it's some kind of bug..
Well i had exact same error and FW solved it, make sure it actually ran, did tool open and it showed successful flash and asked for reboot?Also there are 4 different FW files to flash, atleast for my board (ROG STRIX X870-F GAMING WIFI).