Either the McDonalds by me is fairly lucky or this is far less common than the meme makes it out to be.

It doesn't seem like good marketing - I hadn't had it in years but wanted to try a promo mcflurry a couple years ago, and wasn't expecting it to work, which make me wonder if I shouldn't even bother going. That's the opposite of what they'd want.

But then I went, and have gone probably a couple dozen times since then in two or three years, and it's never been out of order. Obviously I'm not going every day, but across that many visits I'd be likely to catch one if the rate of failure was THAT high.