Could be a bad ESC in the 4-n-1. But before you spend $50 on a new 4-n-1...

Are these E-flite packs that are being charged on the E-flite charger? I had a problem with my charger. They're not very durable. After repeated battery plug-ins and removals the terminal pins on the battery connector tend to break out of the solder on the terminal board. This results in either a charge error, or a false full-charge reading.

Pull the case on the charger and get the terminal board out. Try wiggling the white battery connector, and see if the pins move around in the solder points. If they do, and you're handy with a soldering iron, just reheat the points to re-set the connections. That fixed my problem.