MK138 thermostat board..burned out tracks pictures attached

MK138 relay constantly clicking… on inspection two tracks on the board have burned out, pic attached.
it is used to switch on a heating pad, it is powered by 12v car electrics, the switching side of the relay seems fine and is within the load handling of the board, any ideas or help appreciated.

Only a short or very large current can cause this amount of damage.
Check assembly and wiring carefully. Make sure no external conductors can touch the board.

This is how I wired it…did i do it right?

This is coorect. Make sure to include a fuse.
Don’t know how but it is clear that for some unknown reason the heater current has flown trough the tiny ground track on the board.

Thank you for your help, yes power line has fuse, forgot to add it to diagram.