Cause:
It may be that your robot can no longer find the base correctly in its saved map if the cleaning was not started at the base station and has to create a new floor plan.
Recommendation:
Please abort the cleaning process, take the robot back to the base and move both a bit (max. 0.5 m). Please start the cleaning mode afterwards.
Furthermore, the Kobold Robot locates the base using its sensors. Please consider cleaning the sensors on your robot as a potential solution to the problem.
More about cleaning the sensor: Please clean sensors.