Have you been next to it when it bangs? One possibility that happens with
mine sometimes is that it bangs when turning off because the metal door over
the front of it "pops" out a bit when the suction of the air turns off. In
other words, when the a/c is on it is pulling air in and since the seal
around my metal cover is not "perfect" it snaps back out when the fan turns
off. Just a thought.
It might be helpful for you to be right there to actually see what is
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