I have a 2013 15" rMBP. I occasionally use an external monitor with Apple's DVI-D to thunderbolt port adapter. My model has two thunderbolt ports side by side next to the magsafe port. Well, I really can't use the one right next to the magsafe because the slightest touch or scooting the computer makes my external monitor go completely snowy with no picture. It's not the dGPU because the other port works fine and the system still registers that there is an external monitor connected even when it goes snowy. The port does work, it's just too fragile to mess with. What do you think? Are any of your ports like this?