Ahh, so it's not breaking in then. The ping bms charges my 48v battery to 60.5v, so about 3.78v per cell. This is higher than some other manufacturers recomend. Some say 3.65v is fully charged. 56v, where my ping is for 90% of a ride is only 3.5v per cell. So when the ping bms is balancing, it's during that part of the charge that is overcharged, and the bms bleeds off some power from the highest cells letting the rest catch up.
At the end, the battery is balanced, but slightly overcharged. This overcharge is the surface charge. The instant you draw any power from the battery, it dissapears, and the battery goes to the real fully charged voltage. This will be between 3.5v and 3.7 volts depending on the condition of the cells. If you don't draw any power the surface charge dissipates by itself, and the lights wink out as they fall below the voltage threshold for them to be lit.
I'm not positive of this, but I believe that the lights are merely an indicator of full voltage. In effect, a high voltage light set to 3.75 or something like that. I don't think they actually indicate the balancer fets are open or closed. But while the charger is on, you may see the effect of the fets. A led may light up, and then go off when the bms starts draining that cell a bit.
It is a bit odd that the last light to light up, is the last one to go out. I'd expect a weak cell group that gets discharged more than the others and takes longer to charge would lose it's surface charge faster. No telling what it is, maybe the fet for that cell group starts discharging the cell at lower voltage, and then causes that cell group to charge a bit slow. Or maybe it just has a voltage light that doesn't turn on till a higher voltage. Like maybe the others light up at 3.7v and that one doesn't light till 3.75v. I wouldn't sweat it too much, unless it takes hours longer for it to finally light on that cell group.
But once you unplug the charger, the bms is not doing any balancing. Pings bms balancer does nothing unless it senses an overcharge, so how's that going to be happening as the surface charge dissipates and voltage goes down.