Thank you for your post.
When you manually select an alias under Insert -> Picture, FileMaker recognizes it is an alias and uses the alias to grab the original file.
However, when you run a script with "Insert Picture", you are specifying a file in a specific location. FileMaker will then take that file and attempt to place it into the Container field. You need to specify the exact file when using the "Insert Picture" script step.
I encourage you to enter this suggestion into our Feature Requests web form at:
These web form entries are reviewed by Development and Product Management and considered for future releases. Although I could copy your post and paste it into the web form, there are a couple of questions asked that only you can answer.