In the PnP Modern Search project, we have handled multiple issues and questions related to the "Title" Managed Property and sorting.
People are often seeing something like this Http Error 500
The reason is that they have defined an option to sort by "Title", which should be allright, right?
When we check the properties for "Title" in the Search Schema (in the SharePoint Admin center), we can see that "Title" is neither sortable nor refinable!!!!!
However, we can also see that the managed property "Title" is mapped to "Basic:#10, Office:#2, and Basic:#9, which we can use to fix this annoying issue.
We basically have to map one of the RefinableString properties to those crawled properties.
NOTE: You should map ALL the crawled properties from Title to the RefinableString.
I know that I am going to need to sort by Title sooner or later, so I set up this mapping on each tenant, usually using RefinableString00 and setting the alias to TitleSortable
Once the mapping has been picked up by the search index (when RefinableString00 starts containing values) I can replace "Title" in the Sort settings, and update the Title row in "Manage columns"
And we are back in business again.
I think it's important to limit your use of sorting by Title in search results. It's good if the number of results is small and predictable, but as soon as you're using a search box, the *right* result may be way down the list. But yes, Title simply should have been set up as refinable and sortable from the very beginning of the search schema.
The first managed property I always create is mapping `ows_SiteName` to `RefinableString00`, because *where* something sits is often one of the better pieces of metadata in a search-driven page.