Before you go spending lots of money, just take off the boot trim and have a look. I did this some time ago. The mechanism is not complicated and you might find a easier solution than just replacing parts.
Something might need a minor adjustment.
I was so fascinated by the mechanism I recorded it on my mobile phone. If I can find will upload to youtube for comparison.
Found;
Might be of some use. Each end are the draw down gearboxes and motors.
The white lever has a extra hole for a manual boot release, but its not fitted.
I was contemplating fitting a manual boot release or cheap door solenoid operated by a cabin switch, in case it ever got stuck.