i found out wat happened from an engineer that worked the flight. when the aircraft reached the end of the runway and started its 180 degree turn a status message came up about the main gear steering. after completing the turn the message went away. they tried veering to the right and the message came back up. they a/c returned to stand. a couple hours later they went for the tug and locked out the main gear and pushed it to the end of the runway. after all the vehicles cleared the runway the captain calls back in and says he returning to stand cuz he out of time.