It’s understood the driverless metro was running from Chatswood Station just before 8am today when the train door on a crammed carriage remained open.
Two people dressed in black stood in front of the open door and blocked commuters going near it.
A sign above the door reads “this door is out of service”.
Sydney Metro opened in 2019 and now runs between Tallawong and Sydenham, with 21 stations in between.
Metro speeds reach up to 100 km/h in the tunnel section and up to 110 km/h on the surface track section, according to Sydney Metro.
9news.com.au has contacted Sydney Metro for comment.