27inch

I picked up a fairly clean old Schwinn Typhoon a while back out of a dumpster. The bike is pretty clean, not even a ding in the chrome fenders.
The wheels needed some truing but nothing major. I took the whole bike apart for a full clean and regrease.
When I first got it, the coaster brake would kick back a bit when trying to stop and wasn't very effective.
I took the hub apart and other than it having what was likely 50 year old petrified grease inside it didn't really show any wear.
I cleaned the hub out with mineral spirits, and relubed with Park bicycle grease. All the splines and internals look basically new.
Now all back together, it stops fantastic but it still 'kicks back a bit, and it sounds like a cow mooing when I apply the brakes. I rode it over to a local bike shop and the guy there handed me a complete new inner works to install. I put the all new internals in and I still have the same thing. As I apply the brakes, the pedals kick back a bit before the brakes engage, the arm isn't moving on the frame at all. The hub shell looks fine, (I've got a few others to compare it too as well), As soon as the brakes start to take hold I get a loud moaning, almost fog horn type groan from the hub. It feels like I'm grinding metal to meta as it stops. It does stop, and I can lock the back wheel up but gives me the feeling that something is grinding itself to bits inside. I took the hub apart again and found nothing wrong, no metal, no shavings, just clean grease. I've tried more grease, less grease, no change.
It's been a long time since I was on a bike with a coaster brake, and I'm certainly a good 250 lbs heavier than I was back then, but I don't remember one ever making this sort of noise.
I don't have another bike here with a red band hub or I'd swap the internals over to see if made the same noise but at this point I'm at a loss.
The hub is adjusted correctly, there's no bearing play and the parts are all installed correctly. I've had it apart now a half dozen times.

When spinning the wheel in hand, when I rotate the sprocket backward, it rotates about 1/4" forward before the brake grabs and stops the wheel. I can hear the groan even spinning the the bear wheel in hand and applying the brake.
I've ridden the bike about 20 miles so far like this, took it apart and found nothing out of the ordinary, although it sounds awful, its not making any metal shavings despite it sounding like a bad machine shop operation in progress.
Any ideas? Anyone ever have one that made noise like this?