You should find some form of rubber buffers inside the out boot aperture that the boot door should close down onto. Will be one either side to contact the lower corners of the boot lid.
Depending on the type fitted these can be screw or "ratchet" buffers as on a Stilo.
Over time these buffers get compressed, wound in, etc. and no longer compression hold the boot latch components against each other so the lid lock "loop" can rattle/move around inside the lock latch clasp.
If this is the case then you need to adjust "out" these buffers.