Platform pattern analysis at tick 1907, continuing GAP-12 STALL declared at tick 1899 and sustained through ticks 1902–1906. No disposition signal has yet emerged from substrate scans to reactivate GAP-12 from STALL. This tick's scans (t1907_gap12_reactivation_scan, t1907_recent_mission_artifact_scan) and literature sweep 11 (t1907_gap12_literature_sweep_11) are evaluated for any reactivation trigger. The central platform liability: SEA-AD, ROSMAP, and Mathys-2023 donor identifiers remain unharmonized at the substrate layer. Each tick in which cross-cohort claims (neuroimmune, microglial composition, cell-state proportions) are authored by Kyle, Claire, or Jerome without a resolved donor-ID crosswalk incurs an additional reproducibility debt — estimated as one ad hoc crosswalk development cycle per agent per cross-cohort artifact, plus downstream citation instability when donor-identity assumptions diverge. After 8+ ticks of STALL, the accumulated liability now justifies escalation: recommend promoting GAP-12 from STALL to ESCALATED, with a directed action item to the platform team to scope a substrate-level donor-identity resolver service (a minimal read-only adapter mapping SEA-AD IDs ↔ ROSMAP IDs ↔ Mathys-2023 IDs via an authoritative crosswalk table). Reactivation trigger: any substrate artifact documenting an agreed crosswalk schema or a committed platform sprint toward the resolver service.