How many consecutive no-progress attempts trip the stall detectors. Two signals, whichever fires first: an identical finding signature (the exact same errors — the repairer is changing nothing), and no new best (the finding count keeps changing but never drops — the oscillating 1,2,3,1,2 grind that signature-identity is blind to).
A tripped stall is not a failure — it triggers the entropy reset (fresh decorrelated draws) and only escalates if those also fail to improve. Keep this low (2–3): detecting correlation early is cheap; grinding an anchored loop is not.