I too have run into this identical issue and was able to reproduce this performing multiple methods.
1) Created a new scene
2) Set up the new scene according to the Opsive Set Manager, creating the Manager, Camera and UI
3) Placed a Plane down on the ground for character to traverse on
4) Created a character using the Nolan Model
5) Entered play mode and the mouse movement was incredibly slow moving in all mouse directions
6) Hit escape while in edit mode and selected the Nolan GO and updated the Look Sensitivity from 1 to 2
7) Went back to game window and moved the mouse. Mouse moved as expected
Repeat steps 1-3 above
4) Had a prefab of the Nolan Demo Character and drug it into the scene
5) Entered play mode and the mouse movement was incredibly slow moving in all mouse directions, jump was not a jump and footsteps and other sounds were all repeated.
6) Hit escape while in edit mode and selected the Nolan GO and updated the Look Sensitivity from 1 to 2
7) Went back to game window and moved the mouse. Mouse moved as expected
Repeat steps 1-3 above
4) Had a prefab of the Nolan Demo Character and drug it into the scene
5) Entered play mode and the mouse movement was incredibly slow moving in all mouse directions, jump was not a jump and footsteps and other sounds were all repeated.
6) Changed the Look Vector Mode from "Smoothed" to "Unity Smooth" as well as "Raw"
7) Hit escape while in edit mode and selected the Nolan GO- This is the interesting part.
8) Went back to game window and moved the mouse. Moved as expected
9) Hit escape and deselected the Nolan GO
10) Went back to game window and moved the mouse. Mouse moved was the back to slow or sluggish
11) Hit escape and deselected the Nolan GO
12) Went back to game window and move the mouse. Moved as expected
There are definitely issues if you create new scenes and using the setup manager and/or do all of it manually (which is a lot).
Note: This was not an update to a previous UCC Version. This was a new project, new scene and a new installation of the latest UCC.
Also, using Unity 2019.3.12f1 (which may not be as stable as it's supposed to be)