I need plumbing help. I recently rented a electric drain cleaning machine for the floor drain .?

Everytime I drain the water from the bathtub upstairs the bathroom sink in the basement starts to badly overflow. But I could leave water running in basement sink and it drains O.K. I snaked out the main drain and it still backs up out the sink after taking Bath. It does not back up through main floor drain at all. Need help with this one.