I spent a nearly a year chasing my tail with EPB issues, I swapped the ECU for a used "good" one, chased wiring, banged my head against a brick wall.
I got to the stage of buying a couple of litres of unleaded and a box of matches, but decided out of desperation to buy a new ECU from the local dealer, cost a few hundred quid but worth every penny.
I uded the petrol in my lawn mower and kept the matches dry for another day
Never saw the issue again, not sure if it re-occurred but mechanico-lee would know!
FWIW and from memory the motor each side is driven by a TRIAC in the ECU, which when too much power is put through them then overheat and die a slow death. As it happens, a failing motor draws enough current to cause this, especially if not replaced quickly. I think some opened up the ECU and replaced the faulty components, I suspect others replace and then out their old "good" ones on ebay