Torque formula - underperformance

there is this formula t(in Nm) = (8.3*Current)/Rpm/V
for my example Current = 30 and Rpm/V = 130 → 1,9Nm

Now I did some tests and I get around 1Nm at stall torque.
Any Idea why that can be? Other people get quite close to that calculated value. See for example: OpenTorque Actuator Test (developed by Gabrael Levine) - YouTube (last few minutes)

The Odrive says that the current at the motor is 30A. The power source can definitely handle the power draw (80W measured).