Thanks for this thread. I was going to post a question, but this seems to answer it. One of my four TB47 packs charges to 100%, but rather than the lights all going out when fully charged, light 3 continues flashing on its own. If I disconnect from the charger and press the button, all four lights indicate full charge.
This is not quite the same as the OP issue, but I too will isolate and cautiously test this battery. It only happened after the most recent FW update by the way.
Thanks
Nick