Parkinson Cowan Renown Deluxe Gas cooker- Oven door handle falls off?

The oven door handle, that appears to be the original, keeps falling off. The previous owner has tried a repair using glue and I guess some new self tapping screws. I hav removed the glue replaced the screws with better fitting ones. All is OK until the ven gets hot then the handle comes away from the screws when you try and open the oven door. What is wrong, or what I am doing wrong? Help or advice would be appreciated.