Disco 2 Tailgate doorlock

Doesn't unlock. Have to use string on handle from inside.

Is this the usual new lock required.

If it doesn't unlock then it usually does mean a new lock assembly, however if it's a case of it not opening from the outside then the first thing to check is that all the external parts are working freely. Pop the green oval badge out and give everything a good squirt with releasing oil, work it all until everything feels free and then a dab of grease to keep it all clear of binding.