My Book Live DLNA processes query due to DLNA renderer problems

Putting my hopes on the community here. Old MBL user, happy with the device and uploaded quite a few contents over the years. Lately I notice uploading new music mp3 files to the music share provides errors with metadata (like cover art) in my DLNA renderers. Files are perfectly playable. So, it is the DLNA process that’s making a mess. Anybody know, when, what and how DLNA processes run after a new folder or file is uploaded to the MBL share? How and why do _0_ATN.jpg files get created in the .nflc_data directory under the share? When do the actual numbered TN.jpg files get created? when are these metadatas written to the nflc_database.db file?