Periodically, the REMOVU S1 gimbal may need to be calibrated. There are two kinds of calibrations for the S1.
User calibration, where you can calibrate the S1 by activating calibration mode on the S1 body. You can watch this video to learn how: www.youtube.com/watch?v=BI4oL6JUSgc
Factory calibration requires the use of a computer program to calibrate the S1. You can download the program from www.removu.com/s1_firmware
You can watch this video to learn how to Factory calibrate the S1: