Task starting out of sequence!

Just ran my usual deploy job and something odd happened. example of job

task1
task2
job 1 (constains 5 tasks)
job 2 (contains 10 tasks)
task 3

While job 2 was running its subtasks, the last task, task 3,  of my job ran and completed. The whole job was then marked as completed even though job 2 was still running. Any ideas why the flaky sequence ?

update : reran job again and it was fine!