Search of new folder (library) not working for some users

[AndrewMcKnight]

Hi All, 

My client has requested I create multiple document libraries for them by adding folders and subfolders for each requested topic/subject. The client uses the search function for each document library to either search the document library as a whole or to search the respective (sub-) folder. Creating new libraries/folders has worked successfully since the beginning of the year and we had no problems with the search. Recently, when we add new folders in already existing document libraries, the "Search this Library" search does not show results for certain users. The creator of the library can generally search the library. However other users (owners and members alike) cannot search this library. All the current advice provided by Microsoft (re-indexing...etc.) under the following link (and all relevant links in this area of the site) does not solve the problem: Search results missing in SharePoint Online - SharePoint | Microsoft Docs. Any new ideas out there concerning this problem? Any support would be much appreciated!

[#2]

I think we have the same issue: We have one site where all permissions are inherited from the top of the site, and all users are in the Site Owners group.
Search results for long-established users seem to be OK; newly-added owners consistently have cases where files are not returned in Search, about 20% of the time.
Both Classic and Modern Search are affected, though the Search results differ occasionally between them.
Opened a ticket with Microsoft Support. Reindexing all libraries and the site itself are recommended. Even if this works, (remains to be seen) we have to wait for a weekend to pass before resource-intensive jobs will be allowed to run; and we have no way to confirm that they did run, or if they were successful.