وَجَدَ الْمُرَاقِبُ مِيزَانًا مَعِيبًا، ثُمَّ أَعَادَ فَحْصَ الْمِيزَانِ.
The inspector found a defective scale, then examined the scale again.
The first indefinite mīzānan introduces a new referent; the definite al-mīzān may then point back to that same referent through anaphoric definiteness (ʿahd dhikrī). The adjective maʿīban describes the newly introduced scale.
A second indefinite could allow another scale to be intended. Definiteness therefore shapes reference-tracking and information flow, not merely grammatical surface form.