local (no space) host (or 127-dot-0-dot-0-dot-1) is very slow or unresponsive (and this site doesn't like them as keywords

I have tried searching for other posts on this, but putting "local (no space) host" or "127-dot-0-dot-0-dot-1" into the search box results in a "Forbidden" page. It also messes up this post, which is why I have added the extra words to make them display.

I have a couple of programs on my PC that use ports on local the local machine to display their results via a webpage. I have used them for many years without problem, but in the past few months they have both been mostly refusing to display when I try to open their respective webpage. Occasionally they work, but usually they display partial results, results without the formatting (which might be the same thing), time out all together or  I get a "this site can't be reached" message. The 2 programs are totally unrelated, and the only thing in common is the web address on the local machine. This behaviour is the same on any of the browsers I have tried, IE, Edge, Chrome and Brave

I have tried searching through the Norton settings to see if there is a way of allowing these addresses through, but have been unable to find a result. Does anyone have any workaround to stop Norton breaking these programs?