Robot reports E9; often accompanied by erratic movement or inability to track position.

Safety first: Turn off the robot and flip it over.

Inspect drive wheels:

• Check for wobbling or excessive play in the drive wheels, which can affect encoder readings.
• Clean around the wheel hubs to remove dust that may enter the encoder area.

Advanced inspection (for experienced users):

• Remove the bottom cover to access the drive wheel modules.
• On many Tesvor models, the encoder is integrated into the wheel module. Inspect for cracked encoder disks or loose sensors if visible.
• Ensure the wheel module connectors are firmly plugged into the main board.

If E9 persists: Replace the affected drive wheel motor assembly, as encoder components are typically not serviceable separately. If both wheels appear fine, the main board's encoder input circuit may be faulty and require replacement.