Let's get started!

What you need:
1. Rideable Minecart
2. 2 Solid Blocks
3. Some rails
4. Something that makes the minecart move (or you can hold W, but.. you know, something a little bit faster )

Steps:

1) Place all the blocks like this:

_ _ _ _ _ B
I []
I
I
IO
I
A

"_" and "I" = rails
"[]" = 2 vertical solid blocks
"|O" = a minecart on a rail

2) Ride the minecart
3) press F5
4) travel from point A to point B

What should happen:
When you pass the corner, it will "cancel" F5 mode.

That's the Bug! Hope it will be fixed!