406 hdi brake light switch keeps melting?

Peugeot 406 hdi lx Vreg.I have no brake lights AGAIN!! The bulbs are all correct, fuse is correct, new brake switch (3 times). The white brake light switch keeps melting on the end where the release button is. It melts the button to the point where you cannot push the button. When the switch has been changed the lights work but for no more than 24 hours. Thanks.