Why does our CV drop after we have already given a game away at full price?

Sometimes, the CV reduction is retroactive since the staff can't keep up with all the price changes.

I.e. You give game on Dec 10th and it says full price, but game has been given away free somewhere Dec 5th. When they update the game info, they set all givaways after Dec 5th are 0 CV, making yours 0 (even though it said full price when you were creating it).

EDIT: In your case, I would assume Oppenh4imer answers your question fully (see https://www.steamgifts.com/discussion/8EqEx/why-does-our-cv-drop-after-we-have-already-given-a-game-away-at-full-price#1oLBnOl)

Your CV isn't reduced if the giveaway is made before the date it is bundled/given away for free.
Bundled/Free games are added to the lists by real people, so they are not always available to do so. To prevent users from abusing the CV system by just making giveaways quickly after a game is free, the CV is changed retroactively for all giveaways made after the moment when the game was for free/bundled.

There are two different ways CV can change:

1) Games are in bundles. You citation of the FAQ is concerning this. If your giveaway stats and finished before the effective date, which might be set retroactively, if support only learns of a bundle or high discount after the bundle is over.

2) The base price of the game on Steam changes. Your CV is based on the current price on Steam for a game. If a games get permanently cheaper on Steam, you lose CV. If a games gets more expensive, you gain CV.

Because adding games to reduced CV / no CV list is not automatic. It's manual, and moderators physically can't track every possible way to get game extremely cheap or even free. Then somebody creates a support ticket "hey, %gametitle% was given away for free (or sold extremely cheap) at %sitename% on %date%". And that game is added to reduced CV / no CV list effective from specified date. And yes, it means CV of everyone who made giveaway after this date will go down. I understand your frustration, but that's the only way to fight abuse. So, if you found some game that is selling extremely cheap - don't create giveaway for it, create a support ticket instead, so that it's added to lists in time.