Function prime_duplicate_candidate_rng 

fn prime_duplicate_candidate_rng(
    element: &PoolElement,
    templates: &FxHashMap<Identifier, TemplateData>,
    rotations: [Rotation; 4],
    rng: &mut LegacyRandom,
    scratch: &mut AssemblyScratch<'_>,
)

Consumes the same RNG draws as a failed placement attempt for a duplicate pool element.

Vanilla keeps weighted duplicates, but each attempt exhausts every rotation and target jigsaw before moving on. With unchanged free space, a later identical duplicate cannot succeed if the first one failed; only the RNG draws need to be preserved.