Problems after upgrading to macOS Catalina

After upgrading to macOS Catalina, I found that Middleman did not work, so I upgraded to 4.3.8. My environment was a mess from past installation problems, so I can’t say for sure what the previous version was. Eventually, I got to the point where “middleman version” worked properly. However, when I build the web site, I find that nested layouts are no longer being used. Every page uses the top layout. How can I figure out what is going wrong? Please be aware that I am using Middleman as a tool. I know absolutely nothing about Ruby.

Can you share an example repository on Github?