That error happened to me once ... What you need to do is go to the "main??.cfg" of the car you want to add the engines and do this
Go to the engine section and remove all the code that appears in that image.
If you have more engines, will appear more code ... If you have less engines, will appear less code
And once you remove the code you will be able to work with SLRR Editor
Its the same for all cars
Hope this help 🙂
