Yea you have some bad cells.

I offer some advice on charging batteries and in the past, some of the plane guys disagreed with me. But as a veteran of electric rc car racing with 18 years of experience on a high level including sponsorships from the likes of Ernie Provetti and Trinity, buy a peak charger!

I would NEVER trust my RX packs to a wallwart and some confounded DVM.

And cycle those packs. Often!