Sufficient rest before working the exceedance? Recovery time between shifts adequate (travel home, wind-down, sleep)?
Successive nights / earlies prior to this shift? Cumulative fatigue risk?
Night shifts and early starts before 07:00 carry highest fatigue risk.
Mentally demanding? Long periods of concentration? Natural breaks?
New to role? Persistently working overtime? Health concerns?
Relief by an alternative member of staff, close location / cancel work, reduce manning, relief by supervisor / on-call manager, other.