XB1: Rainbow Six: Siege profile
Hello, this is a mormal occurance with the keymander or any input device such as controller to mouse adapter. These adaptors are limited by virtualizing the joystick of the controller. When you swipe the mouse fast to the side all you are doing is essentially moving the joystick to its max for a fraction and then stopping. Where as when you move it consistently it allows the program to act as moving the joysticm to the max and sustaining it while maxing the stick. Acceleration can be added to the profile to help with flicking, but this can cause you to miss shots or follow up shots when leading a target and the mouse suddenly speeds up.
If you are used to playing on pc this will seem counterintuitive. I suggest downloading a profile from the keymander and load it into the keymander software and set the game sensitivities to the recommendation based on the profile you download. If you need any further help or assistance please feel free to send me a message and I will try to help you with setup.