Firmware was successfully uploaded on April 15th by Andrew
Tested board again to make sure the voltages are consistent
One of the inductors between 3.3V regulator and 5V booster becomes really hot only when Xbee is plugged in
We resolved the issue of the heating inductor by replacing it with another one that is rated at a higher current rating.
The Xbee is now receiving ~3.9V instead of less than 3.3V
We tried to put a diode between the 3.3V regulator and the Xbee power supply pin to lower the ~3.9V to ~3.3V with a voltage drop of approximately ~0.5V from the diode.
The Xbee is still receiving ~3.9V even after that; so, we decided to replace the 3.3V regulator to see if the problem was from the 3.3V regulator.
The problem still exists so we desoldered the whole 3.3V regulator and tested the voltage at the Xbee power supply pin
3.9 V still measured at the XBee power pin even when the 3.3V reg is taken off