Recently my zoom/back button is flip flopping back and forth. I click on zoom then click the back button and it will go to back the flip to zoom again. I have to click it several times to get it to settle in the back position so i can hit..I've cleaned storage, browser, everything but nothing changes..It only started a week or two ago..until then no prob. If anyone else has experienced this or know what i should do please help...very frustrattiing.