Put the summary of the bug you're having here

I was doing a train, and put charcoal in both minecarts wich furnance and began to walk and go into the corner and then on the way up and minecart and minecart with chest were thrown forward.

Minecarts and minecart with chest are thrown forward with the minecart furnace when they enter a ascent.

More details on this vídeo:
YouTube:Minecraft: Minecart Bugs (train)
https://youtu.be/9JwXbTEukQc

Steps to Reproduce:
1. Put minecarts similar images
2. use coal
3. see the vehicles and walk bug in curves and climbs