I found throughout the whole game, whenever you restart a lap the setting will revert to whatever is on the setting sheet for the car; ONLY for setting displayed on your MFD i.e. if you have manually changed TCS or BB via the MFD and leave that setting (TCS/BB) displayed on your screen, when you restart the race the setting will change back to what's in the setting sheet of the car, rather than retain your changed setting.
So after selecting my preferred TCS or BB, I rotate the MFD to radar, and then when I restart the lap the setting will remain as I have chosen.
Even in GTS, at the start of every Sport mode race, TCS & BB usually resets to the settings sheet, so you have to scroll through really quickly and fix it in the 3 second countdown. It's pretty frustrating. I've found that if you go out on track for the warm up and change the settings, it retains at least the BB so only TCS needs to be checked in the 3 seconds before the race.
Maybe someone can explain to us how it's supposed to work?