Batch task doesn't run according to dependencies

During the testing of one of the batch job development, we occasionally encounter one weird problem, the batch job doesn't run according to the dependencies set on them (batch dependencies randomly not working).

We have a batch job, during runtime, it will create several batch tasks, among these task, some of them should run first and some of them will run concurrently, task dependencies are added during runtime.

We did a lot of testing, but occasionally when this happen, we have no idea what has cause it even though the job looks entirely alright, after spending some time on it, we raised a support call with MS Support, this issue has been reported before and it can be found at Partner Source support knowledge base.

Search for KB 2731538 or the subject line "Batch framework does not respect task dependencies in Microsoft Dynamics AX 2009 Service Pack 1", you'll need to download and apply the hotfix.

The screenshot below is showing the Task 3.1, has 3 dependencies, it should run after that dependent tasks are completed. But somehow, it disregard it, even though one of the Task 2 is still executing, Task 3.1 has start executing.