the starting gate at Pimlico

this has been on my mind for a few days, and it makes little sense to me. maybe someone can clarify it for me.
Bother derek, hits the gate when Barbo runs off so hard that he cuts his nose and starts to bleed, his gate doesn't open.
Barboro, however, according to prado, barely touches the gate, he suffers no facial injuries and his door pops open.
it makes no sense, unless the gate is dysfunctional, meaning that the mechanism covering each post is not in proper working order. one is too sensitive and one is not sensitive enough,
i wonder if this gate has been examined, and further if it was set to open like that.