I have seen Sonic Analysis choke on a file it did not like, which made it keep repeating that album. However, I have not seen that behavior in a long time, I think Plex improved error handling.
Still, I would try to identify the file it is working on and make sure it is OK.
You can do this by checking process details while SA is working. It will list the filename in the process info.
You can also do a quick check for some kinds of mangled music files if you look at your music library by file, and sort by length. I’ve had a handful of files which reported ridiculous durations, like 25 hours. Some of those files choked SA.
There are surely other things that can blow up SA, but bad files are the only problems I have had.
If your library is large, and if you have verified that SA does not seem to be getting stuck on a specific file, then I suspect that this is normal. It takes a long time.
