Creaking noise coming from rear with e-brake

There's this persistent creaking noise coming from the rear on my 2006 Prius. Only happens when I'm going into reverse or maybe going over a bump, or jacking the car up while the e-brake is on. It creaks each time the rear goes up with each jack. If I disengage the e-brake, the creak goes away; completely silent.

I've looked underneath with my wife jacking up the car but was unable to pin-point the creaking noise. It's as if the entire rear sub-assembly is creaking. A few things I've already done:

- applied neverseez on the contact points on the rear pads to the rear shields
- applied neverseez to the entire hub surface that contacts the drum
- rear pads look like they have enough material still
- replaced the rear shocks with new ones

What else am I missing? I was think of disconnecting the rear sway bar as there was another member on here that showed his was cracked.

Thanks in advance for any help!