SharePoint modern news webpart "something went wrong"

And so eventually we've found a solution.

Two Search Schema managed properties with the same names or alias.

Thanks to Mike Lee (Boston) and his excellent post about how the Modern News Web part is reliant on search

https://techcommunity.microsoft.com/t5/sharepoint-support-blog/sharepoint-online-news-from-associated-sites-are-not-displayed/ba-p/1254333 

Though my issue was different, I felt there might be something in what Mike Lee (Boston) had documented.

AND yes there was.

We too had a Search Managed Property called AuthorOWSUSER and another Managed property Refinablestring05 with the Alias of AuthorOWUSER.

After moving to SharePoint online, but before modern sharepoint search and news was available we had, as I know many organisations did and do, a customised search page with multiple filters. Refinablestring05 was used on that classic custom search page to provide an Author refiner to staff searching for specific content. We had done this because the search managed property Refinablestring05 could be set to Refine/Sort etc unlike the default AuthorOWSUSER managed property.

As modern search became available we found more value in it than maintaining our custom search page so we moved across to SharePoint online modern search, and all went well for 9 or 10 months until we started seeing the error outlined in this post.

As per Mike Lee (Boston) 's blog post, as soon as I had altered the name of Refinablestring05's alias to be different than managed property AuthorOWSUSER the news web parts started working fine.
So our issue wasn't due to Maori letters in file names, nor was it due to too many managed metadata columns (though they may cause issues in some situations), but due to search configuration.

Here is the Refinablestring05 managed search property after I renamed the Alias to AuthorOWSUSER1

Comment for Modern News Web part team and other Microsoft staff

I think that this issue is a classic example of assumptions not being true and testing being done with test data rather than real tenant setups. SharePoint has been around a long time, so organisations have lots of legacy settings (best practice at the time) which don't have an impact or are even remembered. Then with a small code change, and I couldn't find any mention of changes to the Modern News web part code, weird and non-useful errors are returned to the users.

Please - take a leaf from the OneDrive team's book and make EVERY error useful in that it tells the person who sees it what to do next.