You mean sound was working before, and only after moving house it stopped working? And the TVs you tested now were working with audio through HDMI previously?
You seem to have done a lot of tests, all warranted, only things left I can think of:
try different linemodes (there have been a few reports of higher modes causing sound issues)
disconnect if you have something plugged into the AV1 out/AV2 in 3.5 mm audio port
As your unit was DIY built, I’m not even sure VGP would take it in for repair.
Could be cheaper just buying a new one.