The "Last Activity" event displayed on the task main page is not consistent with the actual last modified event when drilling down on the task within the IM View Submitted Task screen.
All versions of Identity Manager
The application does not currently maintain the millisecond information in the runtimestatusdetails12 table for the Origination Time column and because of that the sorted activities cannot be done accurately.
This would need to be addressed by changing the database schema but that level of change is not something introduced in a CP and would need to be addressed on the next product version release.
Please open an Idea (enhancement) in the online communities for this and let me know if this case can be closed based on the information provided.
https://community.broadcom.com/ideation/allideas