What Caused Voice Alert: Error 4 / Error S5？ 

This error is triggered when RoboVac’s rolling brush is stuck.  This could be caused by the roller brush getting tangled up or stuck by objects on the floor, resulting in the roller brush being unable to spin freely.
 

How Do I Fix Voice Alert: Error 4 / Error S5？ 

1. Remove the brush guard and roller brush to clean the brush, roller joints, joints on the vacuum, and suction inlet. Once all the parts have been cleaned, place the items back into the device and try again.

2. If cleaning did not help, please run the vacuum on hard floors without the roller brush and brush guard to verify whether the error persists when the vacuum is running without both parts.

- If the vacuum runs fine without both the roller brush and brush guard installed, then the problem is most certainly caused by the rolling brush and/or brush guard and you can replace the parts to resolve the issue. 

Brush guard

Rolling brush

- If the error persists when running the RoboVac without the roller brush and brush guard installed, the issue should be with the roller brush assembly. Usually, replacing the roller brush assembly should fix the issue in most cases.
Roller brush assembly