Sonic Analysis can get stuck for more than one reason it seems, but finding a track it does not like may be the most common reason. Assuming that is what has happened to you, you do not need to go through your logs. Look at the processes running on the system and see if there is a Plex transcoder process that won’t die. The file it is working on should be included in the process arguments… use Process Explorer on Windows or ps on Linux to see what is going on.
You might also try sorting your library be track length. When I had bad tracks, each of them showed an absurd run time in Plex… like 25 hours. Every other player showed the expected runtime.
My bad tracks checked out kosher with every mp3 diagnostic tool I had, but Plex still hated them. I even reacquired the tracks from the commercial source… no change! I ended up manually transcoding them to WAV and then back to MP3 with lame. Not a perfect solution, but it was 4 tracks out of my whole library.
