Figma saves layers without an override key with Kiwi's all-ones GUID, so
many siblings share it. The importer stored it as a real key, and export
addressed each instance layer by that key, so two such siblings got the
same derived geometry address and export threw "Ambiguous instance
geometry address". Instance linkage and override path matching also
treated the shared value as an identity. The importer now reads the unset
GUID as no key, through an isUnsetGuid helper that the cleared-style and
default-slot checks share.
The Preline UI kit has 1,165 such text and rounded rectangle layers; after
an edit it now exports and reopens with all 104 pages.