This is the current status of this individual FSM stage (for example pending, in progress, completed, or failed). For that mezzanine-slot (M-slot) endpoint's FSM workflow, stageStatus narrows the diagnosis down to this one stage specifically, which is more useful than the workflow-wide fsmStatus when several stages have already completed and only one is actually causing trouble. A stageStatus of 'failed' here, while earlier stages all read 'completed', would pinpoint this exact step as the one blocking the whole workflow.