I had exactly the same problem with the potentiometer, the tilt switch and to a lesser extent the push buttons: they do not seat properly and often pop out of the board. It's kind of frustrating.
However, what is even more frustrating is the fact that Project 12 needs a line of code added to reset the numberOfKnocks to zero at the end of the loop. Now that is a serious screw up. What's funny though is that the process of finding the fix was enlightening for me. Maybe the error was intentionally included just to force people to think for themselves. It did that for me.