Zanussi Frost Free Freezer?

I have a Zanussi Frost Free Freezer that seems to have developed a bulge in the internal back panel causing the 3rd drawer down not to fully close, this drawer is now forcing open the door of the freezer on occasions. Over the year before this happened I had to clear frost from the bottom of the freezer to allow the bottom drawer to go in but this does not happen anymore and think this may be connected somehow. Has anyone any ideas on whats happening? thanks