Panasonic SA-PT560 Eject problem

[Turnip]

Hi folks,
Have one of these where sometimes it works normally, other times tray won't eject making a loud clicking noise, with the laser assy at the outward end of it's travel. Had a look at the mechanism but couldn't see the problem.
Note ChasHyde stocks lots of DVD bits for this model, so guess problem is common.

Any thoughts ?  Thanks - Chris.