You can replace #!/bin/sh with #!/bin/sh -xu to make the shell print each command before executing. That way you can see what it's doing.
Note that the filebot-watcher is not supposed to act immediately on changes, but wait SETTLE_DOWN_TIME(default: 10 minutes) to see if there's any files that are in the process of being written, meaning it will only process files once they have been not-modified for a little while.
The filebot-watcher is not suitable for non-technical end-users. It's just ~5 lines of shell script, starting with inotifywait(standard Linux command unrelated to FileBot) which prints the messages you see:
I set up https://github.com/jlesage/docker-filebot and after changing the amc interval from 1800 seconds to 10 seconds it started to work exactly as I had wanted it to--wouldn't have been possible without you pointing me in the right direction, so thank you!
filebot-watcher shows no signs of life even after 10 minutes, so I am assuming that I stuffed up the configuration in a non-trivial way.