If the Xiaomi Robot Vacuum S40 cannot return to the charging dock properly, please refer to the following steps to troubleshoot:
1. Ensure the charging dock is placed in an open area;
2. Please check whether the power cord of the charging dock is plugged in;
3. Check the charging contacts. If they are dirty, please wipe them clean and try again.
If the problem still exists, please contact the local after-sales service center for further assistance.