I have not changed the character controller component or the character motor script or the FPSInputController script. It used to be running fine (yesterday) but now the controls become inverted randomly. I do not know how to fix this and I have tried restarting unity.
if you changed anything on the size of the controller you need to change the size of the ground checking.
You can find the settings under Rigidbody First Person controller —> Advanced Settings —> Ground Check distence. After that it worked again by me.