rear brakes locking up

Hello,

You could have the sticking due to a bad caliper or a collapsed brake hose that provides fluid to the caliper.
Keep in mind that when the brake gets too hot it will damage the caliper permanently and it will need either rebuilt or replacement, even if the issue is a collapsed hose. Those brake hoses can deteriorate over time and collapses, creating restriction for the brake fluid to retrieve back when the brake pedal gets released. Creating a sticking caliper.

https://www.2carpros.com/articles/brake-caliper-replacement

I have attached the replacement procedure for the caliper as well as the brake hoses below.

Please let me know of any questions.
Thank you.