Recent button stops working

So, when i put my phone to tablet my "recent apps" button stops working (first from right, don't know if the "recent apps" is correct name for it) there is no cracks on my tablet and the button works fine if used only phone. When touching that it gives light that I'm pushing it but nothing happens. Also after this when i take my phone off from tablet it doesn't work on phone either i have to boot my phone to get it working again. One time i returned my phone to factory settings. After that it worked some time but in week or so problem came back.