That looks really good to me, the cells are staying in balance both charging and discharging.
Remember, the display on the balancer is only guessing at what the battery SOC is based on the voltage it sees, which doesn't work very well on lithium to start with, and really doesn't work when the battery is not at rest. When you are loading it down with the inverter, the voltage drops, so the balancer display drops the SOC because it is only a linear function of the measured voltage. When you are charging the voltage rises, and all of a sudden the balancer thinks the SOC is high.
For now I would ignore the '%' number on the balancer, it is causing more confusion than it is worth. Either use a real current counting battery monitor, or the 'resting' voltage if you don't have a battery monitor.