The shuffle problem is reproducable: Put a huge amount of titles into the default playlist. Play in shuffle mode, everything is ok. Play other content, for example a podcast or internet radio. Select the default playlist again and play in shuffle mode. The playlist has only 60 tracks after that. If I clear the playlist and refill, everything works ok, until doing the above.
Mediabox becomes very slow with huge playlists. Even returning to the shelf takes a long load.