A few weeks ago, we were trying to debug the disappearance of the ability to edit content directly through the front end of a site built using Preside CMS. The admin menu bar was displaying but when you clicked on the quick edit button, nothing happened.
The obvious place to start looking was some JS that was either not being included or erroring in some way. We did have a few JS errors showing in the console, so that lead us down a very worthwhile but ultimately fruitless exercise in fixing these errors.
Our development and staging environments were all working perfectly, it was just production that was playing up. Same code, same OS, nothing obvious going on.
So I ended up viewing the source of the same page in staging and production, and using beyond compare to compare the source code.
Here were the obvious differences - the container comments were missing on production.
So i'd figured out what the problem was, but not how to solve it. Maybe it was Lucee doing some whitespace management, but the settings in the Lucee admin were the same in both environments, and then i remembered we were using Cloudflare.
Ends up, in a bid to keep the site running as fast as possible, I had the Auto Minify for HTML turned on in Cloudflare. An innocuous setting, but this strips out all HTML comments and other stuff.