Minecart with furnace feels like it hasn't been updated or looked into for a long time and feels like a neglected part of the game that most people have probably forgotten, I am also posting other bugs I have found about rail/minecarts.

What I expected to happen:
In the situation attached in picture 1 and 2 I would expect when the furnace is to be fuelled that the minecart (attached by the train mechanic) should follow, and if the ride were to be to violent for the train mechanic, it would simply detach

What actually happened was:
The minecart(empty) ended up in front of the minecart with furnace as shown in picture 3 

Steps to reproduce

1. Build the structure shown in picture 1
2. Place a cart on the closest rail on the right
3. Place a minecart with furnace on the slope(to create the train), this should leave you with picture 2
4. Stand on the minecart(empty) side of the minecart with furnace (or sit in the minecart)
5. Use coal on the furnace to fuel it

[Works on all axis as shown in picture 4]