that bleeder valve has a beveled edge at the end, possible that it's not lineing up right when you tighten it to get a good seal.
did you look at the end of the bleeder valves that you pulled off to see if it was scared at all?
you might have to pull the brake line, cap it off (or plug it) and take a closer look at the caliper when you pull the bleeder valve off.
Poll
