What is wrong with my printer?

thingiverse

I have a Da Vinci 1.0A flashed with repetier using slic3r. It seems that the last few prints of mine have been doing this weird thing. I haven't been watching to see it happen, but when I look at the print, there is a clear line at exactly 40mm up where there is a slight layer shift. There is also a lot of stringing and general nasty print quality. This happens again at 80mm on the phone case. Here are the example pictures. Notice that most of the boat is fine, but the smokestack starting at 40mm is messed up. The phone case attempt ultimately failed completely and turned to spaghetti. But you can see the lines I was talking about clearly. What is going wrong here? One of them is this phone case, which prints on its end: http://www.thingiverse.com/thing:469011 The other is 3D Benchy: http://www.thingiverse.com/thing:763622