I would take this issue to Corporate Consumer Affairs and speak to a manager. Explain what has happened and ask for a brand new replacement camera with zero acutations.
I feel that anything short of that approach will be very frustrating for you. You paid for a new camera and expected it to work. They are obliged to live up to their side of the bargain...especially after 3 failed attempts at repairing it.
Before speaking to a manager briefly outline the camera's problem(s) and the repair failure history and tell Consumer Affairs that you want to have a written account of the problem on record and to make sure your phone call doesn't get lost in the corporate maize.
By emailing or faxing your problem/repair history to a manager, you also have a record of your contact/call.