Inconsistent iPod scrobbles

I've seen a couple of threads where people are having troubles with scrobbling from their iPod, but I don't seem to share all of their symptoms.

I have noticed lately that sometimes some tracks don't get scrobbled from my iPod. Usually they are tracks that I've recently (within the last month) imported into my iTunes library, but not always. I just had this happen, verified that the plays had registered in iTunes after the sync, and tried manually scrobbling (from the Diagnostic menu in the client) and was able to successfully scrobble my missing tracks.

Has anyone else run into an issue like this? Since switching my scrobbling to automatic and managing my iPod with playlists, I've had no problems with managing my play counts. That is until this started happening.