Originally Posted by: BlackHillsHntr 
I went to the mainland with my Lego Ferrari and chose the Sunflower House as my house. I left the house and then quit the game. Not resume, but totally quit the game. I launched the game and was at the Sunflower House but in the 69 Charger, not the Lego Ferrari. I changed to the Fiat Dino and again left the house then quit the game. I re-launched the game and it now has me at the Sunflower House in the Fiat Dino. So try what I did. I also properly shutdown my console when I am done with it. Same thing after any updates.
From memory this is a common thing with the recent Forza games (had it happen in FM7 too), if your current active car when you exit the game is from DLC (or was not part of the base game) then you will be put back in the car that you first chose when you started when next you launch the game (probably something to do with making sure that if DLC is uninstalled or disappears for whatever reason, which is known to happen, that it won't crash the game trying to load content that doesn't exist).