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Most likely hardware issue. You might try running a live Linux USB to see if it still happens in there just to rule out any funky Apple software issues. But the refresh of macOS seems enough there.
Unfortunately it’s not going to be easy if you don’t have AppleCare. Apple solders everything to the main board so it’s not like you can just remove the WiFi card like nearly every other computer out there.
I read this as cow at first and was so confused lol