Thank you for your post.
Did you save the script initially with the field order? Or, did you select the file, the field order and then unchecked the option?
This is what I did:
I created a script with one script step:
Import Records 
I included a sample file, included the field matching, and saved the script. Then, I went back into the script and removed the file reference.
Now, when I run the script, I select a similar file, and the field names match appropriately.