How can I fix a 'stuck Buton'?

Since day one of receiving and using my white version vivo air Blu, it's been a pain in the behind. The 'button' with the 3 stripes to the left of the home 'button'; if you click it, you can see the settings. Now, if you press it and hold it, all the apps you have used show up and you can either select one that you want to use or close it. Now the problem is that every time I want to watch a video or call someone, this 'button' gets stuck and all the apps appear and disappear while the phone vibrates. It's like I press it and hold it when I do not. How can I fix this?