guetzli | Perceptual JPEG encoder | Computer Vision library

I am trying to create a folder action to compress images with guetzli. I am watching the images folder and if there is an image without 'compp' in filename I run guetzli on it. Here is the script. It works great if I run it from automator but when I save it, it goes in an infinite loop and creates multiple version of the same file and adds compp to it, i.e `test-compp.jp, test-compp-compp.jpg'. Not sure what I am missing.

I have just com across https://github.com/google/guetzli - And would like to write a script to run it on all jpeg images in a project on windows.

How would I loop though, all files in the folder and sub folder and get the relative paths to input into the command? Finally as guetzli is reasonably slow is there a way to wait for the execution to finish or put a delay in?

Thanks, Lewis