RCOUT Help. Copter log

I’m trying to understand why one of the motors regulates down. The drone stands on the table and does not fly anywhere. Adjust only the speed. https://www.dropbox.com/s/48c1113b6xr41nw/17-11-18_16-43-24.bin?dl=0

Sounds like you would evaluate a swimmer by having him make swimming movement on a table.