Minecart goes either too far or not far enough when falling

It affected the previous versions as well as the one right now.

 

when you fall off of powered rails with a minecart, you either go far or near the edge, both videos shown were started with  the same method of spawning a minecart and going forward with it, the whole road is made of fully powered rails. It's inconsistent and inexplicable, I want to know where my minecarts will go!! 

what can I do?