The problem is that the media type does not get selected. <ESC>&l0M means plain paper and <ESC>&l7M printable CDs. The printer probably defaults to the main tray because it gets conflicting settings: <ESC>&l14H to select the CD tray and then <ESC>&l0M to select plain paper, which cannot be fed from the CD tray.
This is an upstream bug in the driver. It needs to be fixed by the HPLIP developers at HP.
The problem is that the media type does not get selected. <ESC>&l0M means plain paper and <ESC>&l7M printable CDs. The printer probably defaults to the main tray because it gets conflicting settings: <ESC>&l14H to select the CD tray and then <ESC>&l0M to select plain paper, which cannot be fed from the CD tray.
This is an upstream bug in the driver. It needs to be fixed by the HPLIP developers at HP.