As it has been for many snapshots riding in a minecart past preloaded chunks stops you on track before you hit edge of invisible chunks. you at this pouint cannot leave the minecart but can look around. Also, when reloading map you appear on ground and 3-5 seconds later you reappear in the minecart. Its also seemed to have gotten slightly worse as the minecarts will also randomly stop for no reason as well.