Yesterday afternoon, whilst browsing the site, I came across a small badge challenge that required a player to play the Quick Quiz game and score 100 correct answers to gain a '100 mini badge'.... I played the game, scored 100 answers correct with no break (that's no break in a play session not a no break in correct answers, lol!) only to find, at the very end, that I'd only been scored for 75 correct answers! What a waste of time.... I couldn't find the challenge again today in the challenge list so I decided to play again this evening. 100 correct answers, convert to points and again, only scored for 75!

Is this an old, redundant challenge that somehow managed to glitch its way back into the system, did it appear only on my computer (spooky) or....

Do I need to reduce my coffee/cheese/chocolate intake?

You're not crazy. It's listed 6th down in the Topaz Hall section of the Challenge page. As a Gold Member, you're only allowed to bank 75 Questions per day (this is listed on the banking page, after you click the "convert to points" button in the quick quiz), which is why you only get credit for 75. The mini, however, is for a cumulative question banked total of 100 questions. If you go to the challenge page, you should be awarded the mini, since you have banked 150 total

Edit: Copying directly from the banked questions page:

"Daily Limits:

Regular players get a pool of 100 questions every day, and may bank 20 correct answers per day (max 200 points).

Gold members get a pool of 15,000 questions every day, and may bank 75 correct answers per day (max 750 points)."

And from the Challenge page (I've already completed it, so it looks different than it will for you, but the Requirements are the same):

"Requirements:

Awarded to a player who banks at least 100 correct answers cumulatively in the Quick Quiz game."

When a player banks their questions, they see a screen which includes this information;

So you could answer 500 questions correctly in one day but only be scored for 75. You don't need to answer them consecutively. I often play Quick Quiz in batches of 25 when I have a few minutes. If I have to do something I can come back to Quick Quiz and answer some more. I see your have the badgelet now though. Well done

Since you've played two days (and have a total of 150 correct questions), you should be elgible for the Quick Quiz mini-badge. I believe all you have to do is go back to the challenge page.