Hey Neil,
This is meaningless to me. I don't have Logic Pro to test, and you haven't provided anything that can help me visualize the problem.
So... Why do you have to manually paste?
My first guess is the Pause-Until action isn't finding the image.
If it is finding the image then you might have a timing problem. Keyboard Maestro might be trying to paste a bit before the given text-input box is ready to receive.
Do you get any error message from the macro when it fails?
I suggest installing the Iconaholic Loud or Iconaholic Louder status menu icon, so you can't miss the fact that a Keyboard Maestro macro is running.
Keyboard Maestro Status Menu Icons
Latest Status Menu Icons topics
It would be good if you could post an image or a short video of the problem in action.
If you haven't read this it's worth a couple of minutes of your time.
Tip: How Do I Get The Best Answer in the Shortest Time?
-Chris