/diy/ - Do It Yourself

Guys, what the fuck happened here?

Context:
Wanted to build a 7s battery pack, so got a shitload of single cells and a 8cell charger (eco8, guessing the charger shit the bed, don't buy that shit)
Before building the pack i figure out testing the cells might be a good idea, as some dude has received faulty ones.
So i wire up the cells 2 at a time to both my chargers; an old eco6 and a new eco8.
The eco6 gives me a pristine 4.20 pack, the eco8 poops out this 4.44 monstrosity on the first try.
As insult to injury the bloody thing refuses to discharge them, stating OVERVOLTAGE!
and yes, the charger was just running the regular lipo program, multimeter is fine, both cells measure the same.

And here's the strangest thing; these two lipos don't seem to mind at all, both are flat as a pancake and cool to the touch.