We’re all aware of the broken skill challenges, they usually involve defeating a spectral weapon, which is almost always broken and won’t aggro. This has been the case for over a week now – why it’s taking so long to fix I have no idea, ANet must be aware of the issue.
A quick fix: get rid of the spectral weapons and put in a “commune with” in it’s place. Plop a Veteran in front of it and be done with it.