Just upgraded to 3.6.9042 (P) to be sure this isn't fixed. When I click the three bars at the bottom right of the Compact Player, the ones that switch the right panel between track list, lyrics, and closed, it always forces the compact player to go full screen. Since clicking the restore button sends it back to the main player, I have to manually fix it. Just dragging the header bar does seem to put it back to the previous size, though.