arcing inside inverter

[squiffy]

Hi all.
My Sunnyboy 3000hf inverter was making an intermittent buzzing noise and displaying fault code 77 which often means a relay problem. So I opened the case and gave the relay a tap to see if stuck and the relays close OK, but I can see the buzzing is coming from what I think is the transformers attachment point to the main circuit board.

I've uploaded a video of it here:

Any one had a similar issue or know a fix?

Cheers