To reproduce the bug, you should:

(1)Place a line of rails (except unpowerer powerer_railway) that is long enough

(2)Place many minecarts (may be 100, 300, etc.) on the same railway block.

(3)Walk through these stacked minecarts to make them start moving

(4)Then, the minecarts started to move forever. 

These things is like what has already been said in the MC-14, but when I got the Moion of the minecarts, I was surprised by the motion tag (or in the Java, the deltaMovement field) these minecarts had.The component of the motion can be a number like 1.23456*10^78 or the Infinite.After a shallow research, I found the more the minecarts in the same stack is, the faster the motion growing,for a stack of 300 minecarts, the time from the minecarts being pushed to the motion of the minecarts become infinite is only about 5 ticks.

 The bug may be caused by the pushment between minecarts, beacuse in the sourc e code, the only process realted to the motion between the time motion is set to zero and the time the motion is got (the end of server-side tick).

I think the bug is the cause of the MC-14.In the float-point number calculation, any number except 0 and NaN multiplied by the Infinite produces a Infinite, thus the motion of the minecarts will not be influenced by the drag,

The bug may cause some other problems realted to the motion of minecarts.The power of the explosions created in the collision of TNT Minecarts,for example.

Moreover, a invaild number is dangerous, especally when the number may be saved to the hard disks.If the motion of the minecarts become NaN in sone way, like adding another Infinite with a opposite sign, the entity maybe failed to be saved and reloaded, then make the server crash.