I am having trouble with a model that was built in A 7 and then brought to C 2: At first, everything works fine, i.e. I can open the model in Carrara directly with the "open" command. Then I make my modifications (assigning of shaders etc.). If I then close the drawing and try to re-open it at a later moment, Carrara will always tell me that it is not able to open the drawing: Why does this happen? Thank you for the help.