Just a quick issue for troubleshooting, that 80s sedan (Mercedes 190E look-a-like) body has too much in general. Basic body weighs round about 4 tons, while with some fixtures it is 5t, way way too much. Nevertheless, I tried pushing out some options, still I believe, the issue is basic value for this body - which is ‘WAY too much’. 1t basic would be just fine.
other than that, all seems to be way better than ‘kee’ engine.