That means that your turn and drive velocity code elements do not impact the speed of your robot - the joysticks control the speed.
You can test if it’s a physical issue by lifting your robot off of the ground and running the drivetrain.
A few tests:
- Do all of the wheels spin freely when off of the ground?
- Are you using bearings on both sides of the wheel to support the axle?
- Friction Testing: How to solve Friction problems