[sdiy] EMC mains filter failure - why?

[Julian]

I should have made the point in my earlier post - the filters on two
cabinets failed.  One was plugged in for testing, failed within 10 mins - i
foolishly put it down to chance component failure. The other unit was later
plugged in, also failed in a similar time frame.

Both units had not been used for an indeterminate amount of time, and had,
prior to my use, just been transported from some across the country (not
internationally - same voltage grid)

Would this shed any more light on the situation?

Thanks, Julian