2010 Prius Rear Brakes Locked up

How do the pads look, any evidence of beveled wear? Do rotors have even wear, or conversely, any zone that looks rusty, untouched, in particular on inside face?

Are you aware of the need to orient caliper piston face so that it’s like an X, not a cross? Check my signature for rear brake drag info, on a phone turn it landscape to see signature.

 

It's most likely your parking brake hanging up if you don't have duel braking system (pads & drum). The replacement pads are probably slightly thicker than OEM specs.. when the parking brakes actuate they will sometimes get stuck - until the pads wear down to max. OEM spec. thickness. That happened on my old Honda prelude. It hung-up twice, took it apart both times, couldn't find anything, then went away for good, this also happened after I replaced the rear pads. I did readjust the rear brake cable, all the way to the ends of it's adjustment just to make sure. Readjusted a year later for better grip on hills, no issues.

Hope this helps....