DC current consumption with sense resistor, different measure on oscilloscope and multimeter
You have discovered that the path from ground to the resistor has itself some resistance, and will add to the measured voltage

For this reason there is something called kelvin sense, that is, measure directly at the part with known resistance, with traces that carry no significant current.  https://www.allaboutcircuits.com/textbook/direct-current/chpt-8/kelvin-resistance-measurement/

You can calculate the additional resistance, the current is 750mA and there are 25mV in the ground to resistor section, so cable-connector-soldering resistance is around 0.03 ohms from power supply ground to resistor.

Additionally your load is not constant like a resistor, a motor will slightly or largely change its consumption due to commutations and torque changes, in the Oscilloscope it is seen a ~300Hz component, you want to measure the RMS value which is like the equivalent DC value of a waveform (power-wise) maybe your multimeter or scope can measure in RMS if not your multimeter will add error to the measurement on a not DC signal and probably apply some kind of filtering were you will end getting somewhat the average of the signal