In I hindsight think what has happened is that double cad's refresh is too slow, you cant see what is really there very quickly. I minimised the program and when I came back much later on, all the missing lines had returned.
This happens every time I paste something complex.
As for the scaling problem, the drawing I have been sent was in inches, which it is not supposed to be! Many YouTube tutorials later and I found out how to use the dimension tool and it all makes much better sense.