Do I need to provide the proxy settings inside the location /assets et al. blocks as well?
every X secconds the pop-up shows "Seems we lost connection to the server"
Check out the following faq topic
/manifest.webmanifest is a 401 though CORS crossorigin: use-credentials is set.
Not sure. Can you show a screenshot of this happening? Can you try clearing your cookies and cache? What browser?