I found a bug which seems to come from "17:1 Spruce Wood" and maybe similar stuff.
I'm using Minecraft 1.12

The bug is simple every item that is placed in the delivery to NPC list after this won't be recognized and the name won't be displayed in the quest objective list you can't give the item either to the NPC.

When I look at the quests.yml all items seems to have a :data-1 at their end ( I used string and diamante)
The internal logic seems to be derailed somewhere and the add-on forgot the drop the selector afterwards (I'm a programmer and software developer).

The bug seems persistent with Quests 2.8.7 I also tried the newest 2.9.2 same result.

This Github-Page is no longer supported

use the new one:

https://github.com/FlyingPikachu/Quests

I'm not sure but at least the menu imply for the user that you can do so It actually demands for every single item the NPC id in a list for the delivery. So somebody designed it so that you can do so.

I solved it by simply putting spruce wood at the end of the list. Fixing this would properly only need resetting some vars in a loop.

I think it's actually intended to only be able to have 1 delivery item, if not update me please.
Use stages instead so?
1 Stage per delivery item, that's how we implemented multi Item delivery on our server if it was neccessary. It's not optimal as the player doesn't know directly through the quest objective what he has to bring, but you can tell him by stage messages/npc conversation/denizen/.... :)

King regards.