Finally got a reply as to why they replaced the HDMI board. It was replaced as it was bright & shiny, with nary a speck of dust on it.
Here is what I was told:
"To answer your question on the failure of the HDMI board : The fault is the main dsp ic -the connection of the ic to the board failing – BGA type ic. The newer ic – is connected to the board better and is of a more reliable nature."

That make sense.