How to measure current to a DC motor?
From the photos you provide it is clear that you try to measure current without disconnecting the motor by connecting the ampermeter in parallel to the motor.

An ampermeter will have very low resistance (a perfect ampermeter would have zero resistance so that it doesn't affect the measured current). So by doing that you short the motor (well, actually you short the circuit that drives the motor, but it doesn't matter). This of course stalls the car and btw puts extra load on the driving circuit which can damage it.

You have to connect the ampermeter in series with the motor - disconnect either of the wires and connect the ampermeter somehow like this:

---wire--ampermeter--motor--otherWire