When marking a posted recurring task as completed, only one of the recurring tasks is marked.

Create a Posted Task in GroupWise Calendar
1. Right click in the Task field of a GroupWise calendar view
2. Select New
3. Select Posted Task
4. Select Start Date
5. Select Recurring
6. Select 2 or 3 recurring dates
7. Hit ok, then hit Post
8. Open any of the 2 or 3 recurring tasks
9. Check mark the completed box in the bottom right corner of the task
10.Select - All Instances
11. Select Post
Only the posted task that was edited get's a checkmark in the completed box.  The other 2
posted tasks do not get a checkmark despite the fact that ALL Instances was selected.

This issue has been fixed in GroupWise 8.