On 20/09/2017 06:32, Ron D. wrote:
I agree with Peter. 240/30e-3 = 8K BTW

Metal Oxide resistors usually totally break in half under overload.

Maybe they should have raised it off the board,

They could have not taken into account the voltage rating: See http://www.hkresistors.com/-products...-resistor.html for an example.

240 * 1.4 = 336 V (0 to peak)


I think that is the most likely, HV breakdown , perhaps 2x220K in series
would not have failed but 1x450K would.
The item was stored indoors , no damp involvement.
But it seems a bit odd that dozens of times tested in use and then fails
after an extended period of non-use.
Perhaps stressing while in use, cracking the casing , then a film of
mould or something organic can grow over the MO surface in storage.