When building a rail system in creative, the minecart would travel backward after hitting the corner instead of turning. See the video attached.

Edit: Minecarts can travel around some turns, but not all. When a minecart is dropped one block onto a slope facing perpendicular to the dropping rail, the minecart will act as though there is a turn and go up the slope rather than down; Design in Error-1. Minecarts will also stop on certain corners, but will still make noise as though moving.