When snapping the bottom lock to the top lock, the bottom lock "crosses over"

When I attempted to snap the bottom lock to the top lock, it looked fine from side orthographic view, but once I went back to normal view, I noticed it had snapped to the wrong side of the top lock, like so:

I moved it the same way it looked like it was done in the video: (in wireframe, right orthographic view) box selected the top edges, pressed g to move them up, and hold ctrl and moved my cursor to the front of the top lock. Illustration:

And here's a look at my snapping settings:

Any idea what I'm doing wrong?