Certain content management workflows (creating folder, file geodatabase, adding folder connection, using embedded file explorer) fail when accessed through Catalog or using the content management user interface, but succeed when a geoprocessing tool (Create Folder, Create File Geodatabase) or alternate workflow is used.
Drag and drop the item in question from Windows File Explorer to Catalog (folder connection).
Use a geoprocessing tool, and copy and paste the output location into the input text box, without using the file browser (Create File Geodatabase, Create Folder).