Sounds like the door check is broken. Compare the passenger door to the driver side, there should be a flat metal bar that goes into the door when the door is closed. There are a couple of notches in there to provide a soft stop when the door is partially open, the usual failure mode for door checks here is that they wear out, and those intermediate stops don't grab, but there have been people here who have had them fail all the way. It is not that hard to replace them, and supposedly the same part from a Matrix fits the Vibe, and a Matrix door check will likely be easier to find and less expensive