Hopefully final update on this, I reworked the control board, replaced the triac and 2 resistors.
The machine ran for 3 cycles and then blew the triac again. I repaired the board again and did a detailed inspection of the loom. On a part of the loom at the back of the machine a wire had over time rubbed through it’s insulation. Replaced the whole wire end to end.
Machine now happily running again!