Burnt out Omron relay on Boilermate OV A-Class

Been struggling with my boilermate OV A-Class for a few weeks. Only limited amount of warm water and heating not working.

Upon investigation I have discovered that that Omron G7L-2A-T Relay switch (the grey box next to the two trip switches) has burnt out, and melted the wires that go into it.

Has anyone on here encountered this before?

If so, do you know the cause of this, or is it just a case of the relay failing?

I will replace the relay, but just wanted to see if there was an underlying problem elsewhere that also needs attention.

Any comments gratefully received!!!

There is a mod kit;
http://www.keeptheheaton.com/acatalog/info_gledhill_mip098.html
Mike

MIP 115 270 model
MIP 116 170 model
Mike