Current increases when circuit resistance is increased while measuring black box device power consumption
Your black box is a constant power load (over a limited voltage). When the loop resistance increases with 10 ohm, the voltage over the black box drops and the current increases due to the assumed DC/DC inside it increases the duty-cycle to keep the output voltage inside it constant. More current = more voltage across your 1 ohm shunt.

Does your current consumption increase by about 20% or so?