I try to finish this quest "Cursed Manduri" but the quest seems bugged, it can't be updated,refused or completed.
Here's a screen. I hope this can help.
The quest works just fine, but the displayed step is slightly buggy. You can report to Aurelius (in Eltnen fortress, to the left of Telemachus) and receive your reward.
The displayed quest step and reward symbol above Aurelius' head will be fixed with the next update, but this fix won't affect players who are already in this buggy display state.