Sorry to resurrect an old thread, but I recently started having this problem and wanted to share my resolution for others who find this thread hoping for an answer. For me this had nothing to do with the scraper or settings changes within Kodi. I switched from a different import process to using RADARR which, it turns out, jumps through hoops to preserve the original mtime or "Modified Time" of the files which is what Kodi uses to determine whether a movie has been "recently added". If you start having this problem where you add a new movie file and Kodi scans it into the library but doesn't put it in the "Recently Added" group, check the mtime or "Modified Time" on the file - it's probably not recent. All of the new files I was pulling in with RADARR had mtime dates that were sometimes years old.
Obviously the solution will vary depending on your download process, but you need to do something to update the modified time of the new files coming in. To address this for myself I added a powershell script to RADARR to update the mtime of the downloaded file on import or upgrade. This cleared everything up for me. Hope it helps you too.
if ( $Env:radarr_eventtype -eq "Download" ) {
(get-item "$Env:radarr_moviefile_path").LastWriteTime=(Get-Date)
}