Don't think this is anything to do with new tracks anymore. I have some stuff which has been there ages getting randomly marked. It doesn't seem to be fixed either after a song has been played once with 3.0a7 which I though it might due to a format change or something in the dynamic partition.

It probably just seems like the new tracks uploaded since when I upload them i usually try to listen to them straight away.

Very annoying since I do this.

Have you figured out any pattern to it?