Legoclone I found the error also. Its related to the parts you're using. Everytime I added a fin/wing it does that and I have to reset the default KCT config to scrap the vehicle. I'm currently uninstalling my entire mod list to take out anything not supported, BUT, it also did it with a stock ksp fin. I think part name was basicfin. So I dont know now it seems after my mod adjustment I may need to be extremely careful about what parts on putting on my craft.