Usable battery capacity depends on the capacity of the weakest battery cell and how much of that capacity the battery management system (BMS) allows to be used. So reduced range could be due to either or both. We owners just don't have many tools to be able to distinguish between these two factors. The Android Electrified app, the new iOS mi3 app, and BMW's ISTA+ Windows software provide some data that might be able to shed light on why usable capacity has been reduced.
Your Batt. Kapa. max value is close to the 30% usable capacity loss limit of the battery pack warranty. However, the method used by BMW to measure usable capacity seems to increase the usable capacity a bit for reasons that I don't understand. Some have reported that BMW has updated system software prior to measuring the usable capacity which might have updated the BMS software so that the usable capacity was increased. Or maybe BMW's procedure of fully discharging followed by fully charging the battery pack might increase its capacity a bit.
A different problem is that your predicted range is extremely low, even for Batt. Kapa. max values in the 13 kWh range. Consuming 13 kWh to drive 38 miles is less than 3 miles/kWh. The average lifetime efficiency of our 2014 BEV is 5.2 miles/kWh which is somewhat higher than normal due to our ideal driving conditions. Most i3 drivers seem to have no problem driving 4 miles/kWh unless the ambient temperature is very low or the average speed driven is quite fast. Do you know why your driving efficiency is so low? There are likely things that you could do to increase your predicted range despite the low usable capacity of your car.
2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE