I made a minecart go around in circles. Then I relogged and I expected it to just continue going around in circles on the rails.

Instead it went around in circles, but not on the track.

Steps to reproduce: (singleplayer)
1. Make a circle with rails. (some powered rails so that is has some speed)
2. Make sure the minecart is moving.
3. Log out
4. Log back in
5. Notice that the minecart is moving over the ground instead of the rails.