Hey Terpsychore,
I tried to duplicate your problem in my kit, just built it today, clean version, empty, nothing added but starter content. I broke the links to Name, Kill Tasks and Bring Tasks, compiled to get error.
I then reconnected them no problem at all, compiled with no error.
Did you try dragging a wire from Break AcceptedQuest, Quest(blue) and then typing kill in the box to see if you can read the value of the variable? Get Kill Tasks
If I had to guess there is something you have altered on your end that has killed the link or even changed the variable. I was unable to get the error you had, sorry, I know it can be a pain sometimes working in blueprints. 