The voltage regulator installed on the RedBack is different than the one that is installed on the YellowJacket. The datasheet for the RedBacks voltage regulator says max is 12v, the YellowJacket was upgraded so they could use a beefier voltage regulator.
As I already explained, voltage is not the only thing you need to consider. You need to calculate how much power the regulator is dissipating. The higher your input voltage, the more voltage the regulator drops, meaning it dissipates more power in the form of heat. If the regulator gets too hot, it starts to shut down.
Drawing too much current through an on board regulator is the #1 reason that projects work with USB, but not with external power.