I haev this problem on 1.8 as well, but upgraded to 1.9.0 in case it was just because I was using an old version.

I am using MAC OS/X 11.6 and find that once I have rotated the object, added some supports etc saving it does not save any of the operations I have done on it. When I reload the project file I just have the object laying flat on the work surface.

Is this normal? or is there a setting that I might have to change to get it to work properly?