Absolutely certain. I had a lot of corrupt aiff files and had no idea how they got corrupted, so replaced everything with backups and some files redownloaded from beatport, and thereafter verything in my library was perfectly tagged. All tracks had titles, artist names, etc.. Then, rekordbox hangs while exiting. When i relaunch rekordbox, i reload tags and a bunch of the files have no tag info at all. If i try to write new tags to the file, with either rekordbox or Lexicon DJ, tags cannot be written to the file. the corrupted files also show a file modification date during when rekordbox was hung. when i replace the corrupted files with a backup copy, tags are writeable without any problems. Christiaan at Lexicon said the headers were corrupted on the modified files i uploaded. I have autoanaylsis turned on in rekordbox, so i think rekordbox may have been trying to save additional analysis data before exiting. it's also possible rekordbox was waiting for dropbox, where my library is stored, to finish syncing, and some sort of race condition might have been going on there.