Automation of status change of subitem greyed out when changing status of parent

I am having issues trying to get a Subitem status to change when the parent item status changes. I has a error message when setting up the automation - ‘previous selection don’t include subitem context’ so the subitem status column I want to update is greyed out? It feels like something Monday.com should be able to do, when a parent item is done then mark the sub items as done?

Anyone been able to do this or find a work around, or is this a bug?