Green’s Dictionary of Slang

1. (US) a fool, an incompetent.

c.1965		H. Ellison ‘Neither Your Jenny nor Mine’ in Love Ain’t Nothing but Sex Misspelled 59: He’s clever and pretty fair-looking, but he’s a lox.
1969		N. Spinrad Bug Jack Barron 101: You’re supposed to be pulling the lox out of the hole, not digging it deeper.
2023		(con. 1962) J. Ellroy Enchanters 66: Roman soldier costumes earmarked for the Lox of All Time.

2. (US) in creative terms, something nonsensical, second-rate.

2021

J. Ellroy Widespread Panic 63: Steve the Stud was filing some crime lox [ibid.] 209: This lox [...] which in my view is headed for the drive-in circuit in Dogdick, Arkansas.