Roborock Qrevo edge 2 in two-story house

Roborock Qrevo Edge 2: the dock is on the ground floor. When I run a mopping cycle upstairs, the robot stops after a while because it runs out of water, and it throws an error because it cannot return to the dock, which is one floor down. 
I carry it downstairs. It does nothing. I tell it to return to the dock, and it does so. Then I bring it back upstairs, but it hasn't saved the progress of the interrupted cleaning cycle, so I have to start over from the beginning. And naturally, it can't finish the job because it still doesn't have enough water. Any idea to solve that issue? (I setup the mopping so that the robot use only a fow quantity of water)