TRANSFER PROBLEM WITH DAIHATSU TERIOS

Forum: 

I am writing to report a problem I am facing with my car. I have a DAIHATSU TERIOS 2007 with the attached Vehicle Data. Two years ago while I was driving, the differential suddenly locked without me pressing the right button. As a concequence the vehicle braked and immobilised. After taking the car to the mechanic, the mechanic told me that the transfer was damaged. They replaced the transfer with a used one but the problem remained. By pressing the button (for which I attached a photo), the differential locks, but it doesn't unlock when we press the button for a second time. They also changed the vacuum valve (attached photo) and the button (attached photo), but the problem remains. As a result they removed the tube from the vacuum valve so that the transfer stopped working.
I would like you to inform me if there is a solution to the problem. Could you also tell me if the problem is mechanical or whether there is a problem with the ECU?
I contacted you as I couldn't find a solution since there is not an official representative here in Greece
Thank you in advance!