Same here. I'm not sure I've ever had a bass with an active eq section that didn't hiss a little when you really turned it up. Even my new Dingwall with the Neve pre still hisses a little at extreme treble boost. Is there such a thing as a bass preamp that doesn't hiss at full treble boost? Never had a bass like that!
I just tried my Kubicki. I would say the preamp is average in the noise department. Passive is not as noisy from a treble hiss perspective, but the noise floor is comparable to active if you turn the your amplifier gain up to match the volume of the active setting.
Perhaps there is something malfunctioning in your board? You said the pickup pan did NOT have a center detent, right? If that's true, then something ain't right, and perhaps somebody already tried to "fix" it. This makes me think of something I'm hoping isn't too hard to do. I know the pickup leads plug straight into the board with a Molex looking connector. For troubleshooting purposes, how cool would it be to make a connector that mates to the pickup leads and let's you solder the ends to an output jack? In other words, you'd bypass the board. Even better, the pickup leads would go to a 3-way switch, then to an ouput jack. Just a thought!