Update; Well the guy at Vishay technical support was extremely helpful. Emailed me schematics of the display board and explained in great detail why and how this board failed. My one is an early version so numerous components failed when I connected the power connector to display board when machine was energised. They added a diode to prevent this but was a fail which they admitted. I had performed this task many other times, so that’s what had me puzzled.
I asked him if it was okay to share this info and the schematics if anyone requested. After a week with no answer, here it is.
Never connect power connector to display board when machine is energised. More the wiser...
Thanks for help Mr Strangeways.