Workflow Script with automated tagging

What I want to do:
Every office and pdf file uploaded into a specific directory or one of its subdirectories should be copied to a different location, preserving part of the directory structure.

The problem:
The script itself seems to work as it does what its supposed to when I execute it manually, under circumstances I cant seem to properly replicate it also executes the script successfully but I dont know how to properly debug it as the flow.log has no content (0byte) I changed the path of the flow.log and it created the file but its still 0bytes.
Within the script, the first thing I do is touch a file for a simple check that the script was executed (so for me it looks like the issue is the triggering).

Here is a screenshot of the configured flows:
image

and here is the script which does not seem to be executed anyhow:
touch /tmp/ppl-start &>> /config/log/scripts.log
fdst=${1/$2/$3} &>> /config/log/scripts.log
mkdir -p β€œ${fdst%/*}” &>> /config/log/scripts.log
cp -p β€œ$1” β€œ$fdst” &>> /config/log/scripts.log
touch /tmp/ppl-end &>> /config/log/scripts.log

Is my workflow configuration incorrect, should I do this some other way?
How can I make the workflowengine log to flow.log so I can troubleshoot this?