When I check the check box for a phase/parent task in the Clarity PPM Gantt and click delete, it only deletes the phase/parent task, and not the child tasks beneath it. 

Release:
Component: PPRPRM

In Classic Clarity PPM: When a parent/phase task is checked and not the child tasks beneath it, only the parent task will be deleted. In order to delete the child tasks, the child tasks to be deleted have to be selected individually.

To delete multiple tasks at the same time in the Gantt:
1. Check the check box next to all the tasks that you want to delete
2. Click the 'Delete Task' icon
3. Click Yes to the confirmation message that appears asking if you want to delete the selected tasks

Tip: To delete a large number of tasks, one quick way to do this is to use Open Workbench (OWB). You can highlight rows quickly and then delete them faster then in Clarity.

In the New / Modern User Experience:
In order to delete a phase, the child tasks beneath it have to first be deleted

To submit a request for an enhancement to Clarity PPM, see the following KB KB000044902