I am working on a POC site in V14 sticking to very basic build steps. As the site has progressed it has gotten very slow with either whole pages or parts of the back office not loading. I don't have the skills to debug and trace what may cause this but happy to share my repo.

If you open the browser developer console "F12" when backoffice is megaslow or doesn't work, are there any failed requests? What is your model builder mode? If this is VS on Windows, I've seen some strange cases where running in non-debug ("ctrl-F5") caused strange issues but running in debug ("F5") always worked.

"ModelsMode": "SourceCodeAuto"

That means (afaik) the app restarts every time you save a doctype/datatype/etc (or every time it's saved by a plugin like uSync). Maybe that could be the reason?