Cannot complete Hikari's quest

Describe the problem. Be as specific as possible!:
Tried to do the "Eliminate Water Goblins" quest but Hikari won't let me finish. Says "(null) item inventory is full" when she doesn't give an item.

 Images of problem

If I remember correctly, you actually have to collect 50 cucumbers to complete the quest instead of the 40 that's listed.

Can one of the many quest-whores here verify this?

Yes you need 50, not 40. If you bring up your quest helper I believe it says you need 50. Nexon was trying to "fix" this quest, I guess that didn't happen.

Edit : Nvm, didn't see the Quest Helper in the SS

Yes you need 50, not 40. If you bring up your quest helper I believe it says you need 50. Nexon was trying to "fix" this quest, I guess that didn't happen.

My quest helper in the SS says 40, and the red popup said I was done at 40/80.
Edit: Alright, yeah it's 50. Nvm, guess this can be locked. Just hadn't seen that kind of error before.

This is the one very strange quest where the quest helper (which is usually right, even if the text is wrong) is wrong along with the text. You need 10 more than is stated to complete it.

This is the one very strange quest where the quest helper (which is usually right, even if the text is wrong) is wrong along with the text. You need 10 more than is stated to complete it.

The explanation to why does this happen is pretty simple, though. Quest data splits into two main parts in Quest.wz: Check.img and Act.img.
Check.img specifies what conditions are required in order to finish the quest (Level, day in the week, start\end date, specific items, prequests, etc). The quest helper directly relies on this data, and only on this data.

Act.img is the act needed to be done when you actually finish the quest. A typical "Act" data block specifies you need to remove all the required items from the user's inventory (e.g. if check had "50 snail shells", act usually has "-50 snail shells") and than give the rewards. Although Act.img is contained inside Quest.wz, it almost has no purpose in the client and most of it's data is used by the server.

What happened in this quest, is that Check.img specifies you only need 40 cucumbers (hence why the quest helper shows 40), but Act.img specifies you need to take 50 cucumbers from the user's inventory ("-50 cucumbers"). The server tries to take 50 cucumbers from someone who only has 40, and it throws a common "item inventory is full" error. This error is thrown for almost any problem that occurs inside inventory functions, and also serves as an anti-hacking method (the way it looks to the server, you edited the wz files to make the quest require less cucumbers).