It might just be a random batch of batteries with some flaws. In a previous job dealing with power systems for satellites, we got a bad batch of cells from our long-time supplier. These were cells that get lots and lots of attention during manufacturing, and we did a lot of testing too. Still, the problem only showed up after the satellite was launched.
So... it's not impossible that Specialized might have gotten a few bad ones too.
Still, I'd love to know if they had a problem with the charging circuit or something like that. Lots of ways for things to go bad, and if you work with electronics long enough, you'll see more of them than you wanted to.
