At approximately 02:06 AM on 16th June 2020 during making connection, Roustabout (winch operator) was lifting the DP from the catwalk and floor crew heard a noise from air winch subsequently the Roustabout stopped the winching and applied the brake. Whilst checking the winch the crew found that the lever operated on-off switch which engages or disengages the gear (quick release) is being moved slightly into mid position. Driller put the lever to “off” position instead of “on” position and asked the Roustabout to operate the winch. When the Roustabout release the brake to continue winching, the Drill pipe slid back to catwalk with winch line.