When the redo delay to a quest is completed, the "(Completed)" after the name of the quest is not removed and the show-npc-effects does not wake up.

I think this is intentional as it is to indicate that the quest has been completed at least once. I'll look into making the effect come back, though.

After some experimenting, it looks as though having the effect come back after a quest is completed is not feasible due to how Quests handles the redo-delay.