Studio 1555 boots up but screen stays off - Still

I thought this problem was fixed when I upgrade the BIOS but it's back....
When I turn on the laptop it boots up fine but the screen stays blank (OFF). At first I thought it was the magnetic lid switch staying stuck in the off position. So before pushing the power button, tapping the laptop several times near the left click button, usually fixes the problem - it boots up fine with the screen. But I'm not sure if the problem is switch-related or hardware related for 2 reasons: 1. Tapping the laptop after it's already on, never turns the screen on; 2. After it's on and working I can close and open the lid a 100 times and it turns off and on fine. When I upgraded the BIOS the problem went away for a while but it has returned. Any suggestions? Thanks.