I’m posting this just so it will feature in forum search results as I’ve had a couple of customers miss the blog post on the issue.
If you are running Script Debugger 5 with macOS 10.12 (Sierra) or later, you need to use Script Debugger 5.0.12. macOS 10.12 introduced changes which broke previous Script Debugger 5 builds.
You can download Script Debugger 5.0.12 here.