I'm trying to mount my flat screen. I found a stud using a stud finder and can definitely feel that I'm drilling into the stud but about 1.5-2 inches in, the bit gets stuck. I proceeded with drilling in the screw but it gets stuck at the same spot. I can get the screw in a little further with a wrench but still not far enough to hold the mount flush with the wall. The screws are very long. Any idea what might be happening? There are three different spots on the stud where I have to drill these screws in (vertically) and it's happening with every one of them.