Epb locked on / not retracting. Help with troubleshooting?

[Dougray]

Didn't read the entire wall, but worn cables near the calipers is pretty common on earlier models.

After clearing the codes a few times and trying to enable and disable the epb service mode a few times, the epb eventually did retract. I think, only after I had the engine running. Have an extensive array of codes that related to the epb system and specifically the rear right, so you may be right about a broken wire. It may also be due to low battery voltage as the battery could do with replacement. In any case, I'll avoid using the epb again until I have time to get a closer look at the wiring, test how freely the actuator turns and replace the battery.