Couple of occasion; workflow send mails and set the status as "Complete" and sometime workflow do not trigger mail at all and set the status as "Stopped". Reason why it "Stopped" is because; the instance of Workflow is still using the item and workflow has checked out that item for edit.
Solution:
Wait until the workflow instance finish editing the item. Hence, use below Rules/Condition in Designer workflow
1. Create new steps.
2. Select "Wait for fields to equal value" from Action menu.
3. Click on "fields" link and Select "Checked out to" column name.
4. Click on "value" field link and choose "to be empty"
5. Above condition indicates that Workflow will execute only when item is checked in by last Workflow instance for editing.
Hope this could be useful.
