brakes seem to be locking up

Hello,

This could be due to a faulty brake modulator unit.
That unit controls brake pressure to each wheel.
Internal malfunction like a seized valve can cause brake lockup to any given wheel.

https://www.2carpros.com/articles/how-to-replace-a-abs-controller

I have attached the diagrams for your reference. Also included the testing procedure for that control unit.

Please let me know of any questions.
Thank you.