If I create a new one, everything runs fine.
I think I found it though - After creating a new project and adding the Vehicle C++ caused this.
Add New > C++ Feature > Vehicle > Add to Project
I get an error and when I try to relaunch, the editor spits out the original error.
So I think I have it all sorted now.
So is there any way for me to go back to my original project and remove the vehicle stuffs?
Thanks for you help.