Ibanez EHB buzzing only when pre-amp is on, stops if I touch metal on the cable, gets louder as I move my hand closer to the strings?

Basically the title. I received this bass as a gift, I believe it was open box? The pickups are the nordstrand big splits. The buzzing is completely non-existent with the pre-amp bypassed. It's also fairly silent if the pre-amp is on and the treble boost knob is turned all the way down.. The buzz gets louder as you turn the treble boost up. It's also louder if you have the pickup balance knob centered. None of the other knobs seem to do anything at all, aside from turning the volume down all the way.

If I move my hand towards the pickups, it gets louder.. if I touch the metal on the bridge it gets louder. If I touch the pre-amp bypass switch it gets a bit quieter, and if I touch the metal casing on the 1/4" it basically stops. The cable is brand new since I thought the problem was my other cable at first.

I've tried to do solo research and I see mentions of grounding problems. I also see mentions of shielding problems. Is there a way to know for sure? I'm plugging directly into an audio interface which is pretty quiet with other instruments.