Function already_failed 

fn already_failed(s: &SystemState, defs: &UnitDefs, u: &UnitId) -> bool

§11 as amended in #22 (owner decision, Nov 2): “A unit that has already failed (observed Failed, or not running while it is desired running, when the facts are derived) contributes no disruption of its own”. Read from s, the observation this derivation is made against, never from an incident or from evidence past its stale_after (status ignores that). Unknown counts as running (§10: “Unknown, never Failed”), so a probe that timed out, errored or was abandoned buys no exemption; so does Degraded, Transitioning, an override, or a unit not desired Running.