Reply to Difficulty with S4 buttons

A few months ago I bought an s4 off of ebay, and when I got it, 7 of the buttons didn't work (effect toggle buttons, deck load buttons, etc.). The ones those small circular buttons were always the ones that weren't working. All of the rubber buttons worked fine. So, I sent back my S4 to NI and they sent me back a brand new S4. Which was great, but now after a few days the browse button is trippin out too. I'm really gentle with it, so I don't know what's going on. Has anyone else had problems with any of these buttons or is there another way to fix em?