Thanks all for the replies!
Lets see if I can answer all these questions:
-I do not use ML; not that crazy a question, I've considered it, but no, I'm using factory firmware.
-Longer version of the anecdote: she said she was manual focusing because the camera wasn't focusing, but she thought it was fine at the beginning. Looking at her shots, she nailed some running dogs, so I'm pretty sure it was fine when she got it, and died during that day.
-I have not really tested any of the batteries, since I usually recharge at the end of a day of shooting. But I have fired off 2k frames in one day of ski racing, and not had to change battery. Unfortunately don't remember which battery that was... Statistically speaking, twice as likely to be a third-party one, right?
-battery terminals look clean to me
-both third party batteries AF right down to one bar.
-this OEM battery is ~5months old, can't have more than half a dozen load-cycles. Came with my 7d when I got it, refurb. Makes me less likely to bother returning it... If it is a faulty battery it seems more worth my time to recycle it and get another $15 wasabi power one... They've been great in my gopro for 2 years, and so far so good in this context as well.
Edit: because I got it from canon direct, I'm inclined to think its genuine. Now, it may be refurbed and already have a ton of load cycles, but I think it was in retail packaging...