Can my Neff combination microwave be mended?

I have had my Neff Microwave Combination Oven repaired twice now by the same Domestic Appliance Engineer but it has not worked and he says it is the switch that is faulty and doesn't know what can be done now. Problem: The microwave began switching off after 3 seconds and the oven never warmed up. The door didn't seem to have the positive closing mechanism as before. All lights were working, digi clock working just not doing what it was asked to do. The D.A. Engineer replaced the microwave switch assembly kit and it worked for 7 or 8 months. Problem occurred again and D.A. Engineer repaired it again saying it was the "hinge at the other side that was weak. After engineer left I used it the next day and same problem as initially. So back it went to him. He replaced the switch assembly kit again. Guess what. Problem came back after a couple of days. Before I throw it out the window can you advise.