Just before the end of the section, the <link>'s@targets has "#n3.284" while the <note> above it has "nt3.284" (mind the extra "t"); the latter is the mistake (other notes have just "n....").
This "correction" would give us two elements with the same xml:id value, which the P5 validator objects to, rightly or wrongly. It's an annoying side effect of validating all the examples which affects several parts of this chapter, where an extended example is discussed in several places.
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