ACS AEM Commons Bulk Workflow Manager not working properly for DAM Update Asset Workflow

I have a requirement for creating multiple renditions for asset on upload. Hence, I have modified the OOTB DAM Update Asset Workflow to create multiple web renditions. The workflow runs fine on the assets. I was trying to use AEM ACS Commons Bulk Workflow Manger to run the workflow on the existing assets which are in millions. The issue I am facing is while using the Bulk Workflow Manager, selecting Bulk Workflow Runner > AEM Workflow, the renditions gets created properly. Whereas on selecting Bulk Workflow Manager > Synthetic (Single Threaded) or Synthetic (Multiple Threaded), the renditions doesn't get created properly although the Workflow execution is completed for all the assets.

To replicate the issue:

AEM Version: 6.5.20

ACS AEM Commons: 6.2.0 / 6.5.0 (Tested with both versions)

1. Add web rendition creation step in DAM Update Workflow

2. Make the DAM Update Workflow as NON-TRANSIENT (To have the logs track on workflow execution)

2. Use ACS AEM Commons, Bulk Workflow Manager to execute on the folder of assets. 

3. Select Synthetic (Single Threaded and Multi Threaded)  to test on the assets.

4. Check the asset renditions and test again selecting AEM Workflow dropdown selection in Bulk Workflow Manager page.

Any recommendation and suggestion to avoid this issue. I have seen that the recommendation for large scale assets workflow execution with Bulk Workflow Manager is to go with the Synthetic Workflow (Multi Threaded).

Note: I am intending to run the modified DAM Update Workflow with Bulk Workflow Manager with having much stress to the inhouse AEM server.

If there is any version of ACS Common that doesn't have this issue with the Synthetic Workflow (Single Threaded and Multi Threaded) that would really be helpful.