Thanks for the information regarding this issue.
It has happened on my sisters ix35. a lovely grinding noise from the back left door when locking the car with the remote.
apparently...... yep, a new actuator is required for the bargain replacement price of $309.......
Armed with the information at
Hyundai Tucson - Power Door Lock Actuators Repair procedures - Power Door Locks and way too much time on my hands, i concluded that ...... (for the rear left)
pins 1 & 2 run the central locking lock
pins 1 & 7 run the deadlock.
I opened door, removed trim, found the wire for pin7 (green in this case)
tested with a meter....... yep , +12v when deadlock being enabled.
I made sure door was totally unlocked, and snipped the green wire.
I held in the door pin switch to test...... all good.
I closed door (with trim removed to test..... all good.
Door still locks with normal noise, but i have effectively disabled the buggered deadlock.
The only complaint from my sister is it is too quiet when locking now, and she keeps going back the check .
Probably not an official fix..... but should do for now.