For a long time now, the RCS balancer module for mechjeb has not worked properly. Firstly, I'm assuming the original intention for RCS balancer was to balance the RCS thrusters on craft that do not have them placed perfectly for the stock 100% throttle RCS thrusts. I'm assuming RCS balancer would have accomplished this by throttling down RCS ports that would cause torque.

Mechjeb RCS balancer, however, does not perform as such, and seems to behave rather buggy. For instance, it will refuse to fire thrusters when trying to translate. Or it will fire thrusters, but not all of them, causing torque on the spacecraft.

Before you say "Stock SAS got dis covered," not really. Instead of throttling down the proper ports, it fires other ports to counter torque, which is very bad die to excess fuel consumption. This also doesn't seem to work on craft like the KSO shuttle, which end up with too much torque for the stock SAS to handle due it improper RCS throttling.

In the screenshot below, RCS balancer is on, RCS is on, and nothing else is on. I'm trying to translate the craft to the right, but the RCS thrusters are not firing with RCS Balancer on.