I got the issue when I upgraded to v1.2.0，It works if I cancel the task and restart it.
I recommend searching the forum for existing issues, such as Pipeline doesn't start until stopped and started again.
I can confirm there are no known issues with Drone 1.2 since we run this version at cloud.drone.io and have not experienced any problems matching this description.
@bradrydzewski Thank you，I have found the reason , the process of build is not been stoped, it is my problem.