Azure Rest API CI task completes but stuck on non-closing STDIO lingering process

Question

As part of CI pipeline on ADO, I make REST API GET calls to get a list of requirement work items objects and a list of test results object. I sort and match the list and then I do multiple POST call to add information from that list as a attachment of my ADO test item object. Everything is done thought the ADO Matlab plugin task by using system function to execute curl through the command line via Matlab. Everything seem to work, I see the attachment on every test uploaded well and it even prints ''Done'' after all curl POST request to indicate, I'm done with my Matlab script.

I would expect the ADO CI job task to complete and pass to the next task in YAML file. But after running for 5 mins and completing everything, the job task stall and keep running for another 10h(Max ADO pipeline time)

The STDIO streams did not close within 10 seconds of the exit event from process 'C:\agent_work_tasks\RunMATLABCommand_28fdff80-51b4-4b6e-83e1-cfcf3f3b25a6\0.6.3\bin\run_matlab_command.bat'. This may indicate a child process inherited the STDIO streams and has not yet exited.

Any Ideas how to resolve this bug?

What I Tried:

1. I tried to run my script locally, I saw all my curl outputs via my matlab command window, but I saw that upon completion it opened a empty command prompt window.

2. looking for similar incidents and tried closing all processes(#4) as indicated here: https://developercommunity.visualstudio.com/t/the-stdio-streams-did-not-close-within-10-seconds/523146

3. I tried adding pause/wait in matlab script or via system command call to give time for asynchronous process to complete.

4. I added quit to my matlab script, and I tried using Taskkill/IM cmd.exe to kill all open command windows when my scripts ends.

Both didn't work on the CI pipeline. it still runs forever until i manually stop it or it reaches max time.

Error message & partial log:

2022-04-04T18:39:45.6947848Z curl -u :**ADOPAT** -X POST -H "Content-Type: application/json" -d "{\"stream\":\"***B64 encoded content***\", \"fileName\": \"requirementPath.txt\", \"comment\":\"Testattachmentupload\",\"attachmentType\":\"GeneralAttachment\"}" http://dev.azure.com/{organization}/{project}/_apis/test/Runs/**runID**/Results/**testResultID**/attachments?api-version=6.0-preview
2022-04-04T18:39:46.3140720Z 
2022-04-04T18:39:46.3141125Z status =
2022-04-04T18:39:46.3141240Z 
2022-04-04T18:39:46.3141367Z      0
2022-04-04T18:39:46.3141523Z 
2022-04-04T18:39:46.3141598Z 
2022-04-04T18:39:46.3141697Z cmdout =
2022-04-04T18:39:46.3141781Z 
2022-04-04T18:39:46.3141992Z     '  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
2022-04-04T18:39:46.3142311Z                                       Dload  Upload   Total   Spent    Left  Speed
2022-04-04T18:39:46.3142510Z      
2022-04-04T18:39:46.3142760Z        0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
2022-04-04T18:39:46.3143126Z      100   354  100   139  100   215    269    417 --:--:-- --:--:-- --:--:--   692
2022-04-04T18:39:46.3143506Z      100   354  100   139  100   215    269    416 --:--:-- --:--:-- --:--:--   692
2022-04-04T18:39:46.3143948Z      {"id":**attachementID**,"url":"http://dev.azure.com/{organization}/{project}/_apis/test/Runs/**RunID**/Results/**testResultID**/Attachments/**attachmentID**"}'
2022-04-04T18:39:46.3144224Z 
2022-04-04T18:43:06.5720937Z done
2022-04-04T18:43:29.0053832Z ##[debug]Exit code 0 received from tool 'C:\agent\_work\_tasks\RunMATLABCommand_28fdff80-51b4-4b6e-83e1-cfcf3f3b25a6\0.6.3\bin\run_matlab_command.bat'
2022-04-04T18:43:39.0075174Z The STDIO streams did not close within 10 seconds of the exit event from process 'C:\agent\_work\_tasks\RunMATLABCommand_28fdff80-51b4-4b6e-83e1-cfcf3f3b25a6\0.6.3\bin\run_matlab_command.bat'. This may indicate a child process inherited the STDIO streams and has not yet exited.
2022-04-04T18:43:39.0076952Z ##[debug]The STDIO streams did not close within 10 seconds of the exit event from process 'C:\agent\_work\_tasks\RunMATLABCommand_28fdff80-51b4-4b6e-83e1-cfcf3f3b25a6\0.6.3\bin\run_matlab_command.bat'. This may indicate a child process inherited the STDIO streams and has not yet exited.
2022-04-05T04:10:04.2626714Z ##[debug]Re-evaluate condition on job cancellation for step: 'Matlab Rest API Test Update Action'.
2022-04-05T04:10:04.2919553Z ##[error]The operation was canceled.
2022-04-05T04:10:04.2932116Z ##[debug]System.OperationCanceledException: The operation was canceled.