Why redesign? The device clearly performed well enough under "normal" conditions, whatever it is. It was not a "normal" thing to sweep it with a powerful microwave transmitter from time to time.

Incidentally I know the rest of the story: after they found out the reason, they simply moved the box to a better position, having consulted with the airport management of course.

And, btw, this story was told by an EMC instructor, as an example of equipment which passed all reasonable EMC and other compliance tests for that sort of equipment, and still failed under a nonstandard situation.

And, in industrial equipment deployed in a hall with a high density of powerful machinery not always closely following all the regulations, this might happen more often than elsewhere.

YMMV (and that was my point, incidentally).

JW