When pressing the disc tray OPEN/CLOSE button is there a click or not?
If there is a click the OPEN/CLOSE mini-switch is probably functioning correctly. The mini-switch is operated by the lever behind the front panel OPEN/CLOSE button as indicated by the pencil in the first photo. The OPEN/CLOSE mini-switch is located on the chassis motherboard as indicated by the pencil in the second photo. (The photos depict the similar DMR-EZ17 model.)
If there is no click the OPEN/CLOSE mini-switch has probably failed. Replacing the mini-switch is a simple soldering job but requires removal of the chassis motherboard from the machine.
A replacement mini-switch may be purchased at a nominal price from Panasonic's National Parts Center. The link to the DMR-EZ27 parts list is found toward the lower right of the following page:
Less likely causes to DVD Drive mechanical malfunctions may come about by a disturbance to the DVD Driveâ€™s wired power connector, the ribbon cable between the DVD Drive and the Digital PCB or a problem with the Digital PCB itself, as seen in the third photo. The DVD Drive on-board controller PCB, as seen in the fourth photo, may also be the cause of DVD Drive mechanical problems. I have addressed remedial procedures for DVD Drive disc tray misalignment at the AVS Forum.