Hi,
normally scene should not be changed when rendering, so this is a bug - it should be fixed in next daily build.
For now you can workaround this problem by enabling "Use new implicit conversion" in development/experimental section of render settings (see
here how to access this section). This will enable new implementation of c4d materials conversion that does not have this problem (but is still in development, so there might be another issues).
EDIT:
Another (and simpler) workaround would be to simply render to picture viewer till next daily build is released as this bug should only affect rendering in viewport.