Four rules for duct and pipe fittings (connector count vs Part Type, primary connector on X, elbow angle parameter) were checked by nothing; each looks fine in the Family Editor and only fails once the fitting is loaded and a run is drawn through it.
From the Grok pain-radar digests, Oct 28-29 2026 (Oct 28 8:41 AM ET through Oct 29 early-morning Haitch editions). Verified live 2026-10-29: issue/PR read; title and state confirmed.