I've just finished 9398 4x4 Crawler. The rear motor works properly, but the front motor doesn't: The wheels seem to be locked, although they spin freely when I turn them by hand. What could be the problem?
In my version of the set, there is an extra sheet pointing towards this particular piece. It is not a mistake in the instruction, but they put in an additional picture to clarify how it is done correctly.– AziraphaleMar 14, 2017 at 9:41
Check if Cross Block 90° that is placed in step 53 of instruction book 1 is in the correct orientation with the round hole placed over the motor axle.
Mounting it the other way will prevent rotation of the motor.