When you say "secure and open methods" do you mean that you have specified external storage for the container fields?
If so, "by reference" is not the option that should be used with files stored in that container field.
You might try setting up non external storage for the field and see if importing the data now works.
It's OK I- figured it out. I was trying to load images from an auto-backup - which didn't have the same folder hierarchy as my original. duh. But thanks for taking the time to reply.