Quick potential bug report / race condition report from me - something I've been getting ever since I started using the plugin intermittently, but it's caused me a lot of grief today as I've been tidying up my album art.
Firstly, let me explain my usage. I have around 15,000 FLAC files, all of which I have an m4a (AAC encoded) copy of. So each m4a file is marked as being linked to it's FLAC master using your plug-in and I'm not using the ASX files. I do this to keep the metadata between my master" FLAC files and compressed files in sync.
My options panel is set to sync all data changes for each, except for information specific to the m4a and FLAC file (bitrate, encoder used, etc... ) and one of the things I try and synchronize is Album Art. I like to tag all my file with Album Art, and optionally keep a folder.jpg in place too, but I'm less worried about that. My preferences are therefore set as shown here :
The problem I get is with Album Art. If I try and tag a whole album (of FLAC files) with Album Art, often using the "Lookup from web" wizard in MM3, I click auto-tag and will see the process bar in MM report "10 tracks to be tagged". Then, a second or two later, the plugin kicks in, and I see "Updating 0/10 appear" as expected, and the number of tracks to be tagged go up to 11.
Here it's about 50/50 what happens. On a good day, the number of tracks to be tagged goes up to around 18-19, the plugin completes, and the number of tracks to tag slowly drops to 0. Why so slow ? Well, FLACs are quite big files to tag, so take time, and my files are stored on a NAS. A very fast NAS, with gigabit connection, but nonetheless is a factor of 3-4 times slower than tagging local files, I find.
But on a bad day, it now hangs, as shown below. What's more, MM will not exit or close, and the only way out of this is to kill the process via task manager. Any further attempts at lining up tagging during the session just get stuck in this queue and never complete. So somewhere, I think the plugin and MM are getting a deadlock, possibly on the database, I'm not sure having not delved into the internals of MM myself (maybe I should one day !)
My workarounds are to turn off the automatic synchronizing, only invoking it manually when all the master FLACs are done tagging (or half-way through being done... as long as a few are processed, the deadlock doesn't occur). Or to turn off Album Art in the synchronizing, which means the deadlock occurs a lot more rarely, but still does occur on occasion; this has been the case for the last year or so, where I've just been tagging non-album art fields.
So therefore I've only seen this deadlock once, maybe twice a month at most in the past. Today, tagging 20 or so albums with art, it's happened around 15 time, hence the prompt to get me to report this issue. Suspect my usage of your plug-in my not be the one it was designed for, and my set up is slightly unique, but would be cool to get to the bottom of it if possible ?