Why do my rear brakes chatter?

When I got the truck the parking brake did not work. I had my local mechanic look at it. He freed up all the moving parts. Now the parking brake works. Ever since then I get rear brake chatter when I come to a stop. I rechecked all the moving parts are working. It does have brand new shoes and drums

 

Experienced the same
-my taco
-my neighbor’s 08 Chevy

search “warped new rear drums”

I wouldn’t have believed it until I experienced the same thing 2 times….2 manufacturers
My neighbor refused to acknowledge…
Until we put his old drums back on
Guess what……perfect

Freakin BS