Dream X40 second floor mapping issue

I tried mapping the second floor, but after about 7 minutes the robot started moving only about 1 foot at a time and rotating repeatedly. It seemed like it was lost and kept repeating this pattern. Even after 15 minutes, it didn’t complete the mapping.

I then moved the base station to the second floor, and the mapping finished successfully in about 5 minutes.

My concern now is that both maps (main floor and second floor) show a base station. How should I proceed with cleaning in this situation? Was my mapping approach incorrect?