A puzzle inside a puzzle

In Rabbit Redux, Harry Angstrom has gone into his father’s trade, operating a Linotype machine. There’s a couple of passages in the book where John Updike reproduces the lines of hot type that Harry sets for a local tabloid, including his mistakes. So we come, in Part II, to this passage, typed while Harry is particularly agitated:

Police authorities  revealed Saturday  that they are
holding for questioning two black minors and Wendell
Phillips, 19, of 42B Plum Street, in connection with
the brutal assault of an unidentified sywsfyz kmlhs
the brutal assault of an unidentified elderly white
woman late Thursday night.

The letter substitutions make sense when you look at Ottmar Mergenthaler’s keyboard: Harry’s left hand has slipped one column to the right.

Except for one thing: sywsfyz should be sywsfyq. The key to the right of y is q, not z. My text is the Everyman Angstrom tetralogy. Where did the mistake creep in?