In this scenario it is possible to have a milestone task with assignments and actuals posted to it.
This can happen if the task is initially not set as a milestone and a transaction is posted, then the task is set to a milestone before the transaction is posted back to the assignment (Import Financial Actuals job.)
STR:
1. Create a task with no assignments
2. Create a manual transaction for this task.
3. Post the transaction (do not run Import Financial Actuals job)
4. Mark the task as a Milestone
5. Run Import Financial Actuals job
Expected Result: Posting the transaction back will error as the task is now a milestone
Actual Result: Transaction posts back to the milestone task which now is a milestone with assignments and actuals.
Workaround: Contact support for resolution.
All Clarity versions including 16.4 and 16.4.1
Fixed in 16.4.2.