Robot vacuum reports E4 and stops; often described as side brush error or side brush stuck.

Safety first: Power OFF the robot and turn it upside down.

Step-by-step:

• Remove the side brush: Use a small Phillips screwdriver to remove the screw holding the side brush (if present) and pull the brush straight off the shaft.
• Clean the shaft: Remove hair and debris from the motor shaft and around the base using tweezers. Wipe with a dry cloth.
• Inspect the brush: Check the plastic hub for cracks or warping. Replace the side brush if damaged.
• Test the motor: With the brush removed, power the robot ON and start a cleaning cycle. Observe whether the side brush motor shaft spins freely. If it does, reinstall a clean brush and test again.
• Internal inspection (advanced): If the shaft does not spin, remove the bottom cover and locate the side brush motor module. Ensure the wiring harness is firmly connected to the main PCB. If the motor is seized or the board is burnt, replace the side brush motor assembly.

When to stop: If the motor does not run even with a known-good brush and secure wiring, replacement of the side brush motor is necessary.