Moldy/mildew unboxing?
I had this problem before in 2020 buying an intel 13" pro, it turned out only to be the cord. Every replacement cord had the same problem and I was spending way more time on tech support getting replacements than its value.
Now I am about to unwrap a my new M1 Air. It's in the plastic and I already smell the mold!
I pray it's just the cord. But it's so strong it permeates the box and the plastic.
I ordered the first one to Montana, and this new one to California. Where were you when you got a moldy macbook?