Right now I am playing the entire album "Modest Mouse - Lonesome Crowded West" if you were to view my "Recent Tracks" on last.fm you can see that pretty much the entire album was played, and logged on Nov 13th. But right now I have already listened to almost the whole album again Nov 15th, and not one of the Listened(L) tracks show up in the log.
Not really a way I can explain to replicate it, I just turn the player on and start playing tracks, I don't know if it may have anything to do with how I go about playing them, I usually have to shut off the player after I listen to a few tracks and someone needs to speak with me, then I just turn it back on and click the pause/play button to restart playback, but still no log entries.
(I just tried skipping back with the skip track button and it is still not logging it is real difficult to say what I think gets it to log or not, usually skipping back and forth fixes it, but right now it doesn't seem to want to log at all)
some days are certainly better than others no idea why.