@method1 are you definitely on 9.5.20 and not 9.5.21? If so, then I wonder if the problem is MacOS 10.13.4 rather than the Cubase update?
Out of interest, I went back to 9.5.20 via time machine and still had the problem with projects created in 9.5.21, but not new projects I created in 9.5.20.