Steps to reproduce:

1. Create trigger with "allow manual close
2. Create Trigger Action with a "Recovery operation" (mine was to run a remote command)
3. Cause trigger to activate and raise a problem
4. Click "Ack" link
5. Tick "Close problem" box and click "Update"
6. Note that "Recovery operation" did not execute even though problem is now resolved
7. Now click Ack link again and tick "Acknowledge" box and click "Update"
8. Note that "Recovery operation" has now executed

Expected:
Since the problem can be "resolved" without being "acknowledged", the "Recovery operation" should execute at the point of the problem being closed.