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Join Date: Feb 2015
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Sometimes when BPs don't scan properly, GAs will look at the BP and mark you boarded by entering your seat number, e.g. 2A.
If they're not paying attention to your BP, that could be part of it. Although how a second person gets on with the same seat number, I'm not quite sure. Perhaps it also flags red and the GA simply attributes it to a system error since the person's BP is indeed valid. But I'm speculating now.