Hi. My name is*****’m a camera repair technician with over 25 years in the business and I'll be glad to help you with your question today.This sounds like dirty switch contacts. Sometimes greases or other foriegn substance can contaminate the surfaces an cause an intermittent problem.The solution is to remove the top cover and clean the switch. The catch is, you need to be a technician to do this. Too bad your not in the States, I could offer you a low cost service but I'm sure you can fin one close to you. Below is a link to a directory of repair shops, one of which should be in your area and able to help you.