Glowworm PCB recurring problem

[SandyLyon]

18 months ago I replaced the PCB in my daughters Glowworm Ultimate 50FF boiler as the relay had started "chattering"
I have just had to replace it again because of the same problem, both replaced boards show a "blackening" in exactly the same place.
Is this a fault with this particular boiler / board or is there something else causing them to fail.

 

[ollski]

Boards are pretty flaky but the heat staining doesn't mean a fault in that area.

 

[SandyLyon]

Got a brand new PCB so we'll see how that goes.

While searching for an exchange service I came across Adlink who had this photo on their site, looks familiar,