Well, there are settings in Go4 to set when it will do what ever, but I thought that was only initiated with a low setting 10-20%.
Have you tried discharge and recharge? How about cell voltages, are they equal? I would inspect the battery externally for any bulges, compare with another, the surface should be nice and flat. Install the battery in the AC and link to the RC and then to Go4, check the battery cell voltage, let it just run a while, until it starts to drop a bar, the look again. I have read about the guy whose P4 dropped out of the sky, with battery remaining. But the log showed low cell #4, it was way off, yet the battery reported like 70% then 50 then at 30% or something it just shut off and fell 12 meters.
I think that I would really want to run it through a cycle, watching the cells, maybe hover it at 3 feet and just watch the cell voltages.