1-
Select Multiplayer -> Split Screen -> Press Start on a second controller / keyboard -> P1: Select any team & driver -> P2: Select any team & driver -> Any Race Settings -> Any track.

2-
Once on track P1 pause and select Options -> Driving Controls and change Control Profile to another option and then back again. Exit back out of the Pause menu.

3-
P2 pause and select Options -> Driving Controls and change Control Profile to another option and then back again. Back out to Pause Options, select Quit To Main Menu -> Yes.

4-
You should now be able to save again.