Qualiddy control

I use a heap of batteries at work, hundreds of them. We buy them in bulk to get a decent price, mainly AA’s but all sorts from tiny button cells to 200 amp hour sealed lead acid batteries.
Anyway we recently bought a case of Varta AA batteries. The other day we had something that took 3 AA’s batteries and failed in just a couple of days. A bit of head scratching and a multi meter showed that one of the batteries was reversed in polarity- never seen that before.
So I went to talk to the guy who uses the bulk of the AA’s to let him know, only to be told he already knew, and it was around 1% that were faulty he was testing each battery before using them…Not going to be buying those again.
I guess the takeaway is not to take anything for granted, not even something as simple as a battery.