E70 Parking Brake Issue

[JamieOS]

Hey guys, my dads 2011 E70 X5 Facelift has been plagued with parking brake issues over the last few years and its gone once again. I'll try and break down the issues in a timeline and hopefully someone might have some advice on what to do next.

The first time the parking brake failed, it was parked on a hill and we were both nearby and head this really loud metal on metal sound. It seemed like it had tightened itself all the way up. We managed to pull the release and get it rolling. I took the cover off the actuator unit and found the motor had would itself full tight. Once I managed to break it free and unwind it, I clipped the little blue force sensor back in, put it all back together, cleared the fault light on the dash and it worked fine for about 2 weeks or so.

After 2 weeks it failed again doing exactly the same thing. Being parked with the parking brake on and randomly over tightening itself. Pulled the release again and left it like this while we decided what to do. Genuine units are around 1400 Euro here so we went for one off Amazon for 175. I fitted that and retained the old cables as it was easier to keep them fitted. This Amazon unit lasted for about 3 or 4 months before doing exactly the same thing. Luckily Amazon honored the guarantee on behalf of the seller and gave a refund for it. Because the Amazon unit was just overall bad quality, the release cable for it actually didn't work so we had to cut one of the existing cables to get the X5 moving again. I decided to order an Aliexpress force sensor as it was only 45 Euro. That took about 2 months to arrive and when fitted to the original actuator module, it required the actuator module to be recoded by a specialist as we had left it unplugged while waiting for the new force sensor. I also fitted a new cable to replace the side we had cut.

This fix lasted for nearly a year before once again doing exactly what it had done in the past and overtightening itself and getting stuck on. This time we decided to just get a used parking brake actuator from a car dismantlers and used the force sensor from it in our original parking brake actuator so it wouldn't require coding, as I cannot for the life of me figure out how to get ISTA to work properly and communicate with the car. Anyway, this fix lasted a few more months before finally doing, you guessed it, exactly what its done in the past and overtightening itself while in for its yearly inspection no less. The garage managed to pull the release, however strangely when my dad got home, he applied the parking brake and it seemed to work fine and the X5 wouldn't move while in Drive and it also released when he switched it off. However the fault light has come back on and its not working more. I will be doing some investigation into it over the weekend. Hopefully it just needs the fault code cleared as unlike all the other times, it worked after the emergency release was pulled. Hopefully its just as issue with the plastic gears or something as I have spares of those from the unit we got from the car dismantlers.

So if the unit is faulty, I'm just wondering what to do next. I've run out of ideas and I don't really want to admit defeat and shell out the better part of 2k to the dealers to have a new genuine one fitted. Any advice would be greatly appreciated.