Left rear brake has locked up

Hello,

It sounds like the brake is locked up due to the caliper being stuck.
One of most common reason for the caliper to stick is having a bad brake hose.
Over time the rubber brake hose can collapse on the inside, this creates restrictions, and the brake fluid is unable to go back when the pedal is released, that leads to the caliper sticking.
Keep in mind that when a caliper sticks it heats up the pads, rotor.
The excess heat can damage the caliper so replacement of the caliper along with the brake hose is recommended.

Here is a helpful article:

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

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.