Temporary poor positioning signal, or incorrect positioning of the GNSS antenna.
If it happens occasionally, it may be that the positioning signal is unstable. You can manually put the mower back onto the charging station.
If it happens frequently, then it is possible that your antenna or charging station is placed in the wrong place where the positioning signal is poor. Move the charging station to a more suitable place. You need to remap the whole boundary after relocating the charging station.
If the error persists after following the troubleshooting guide above, please don't hesitate to contact us for further diagnosis or your dealer for after-sales service.