So my friend and I were playing on our 19w09a world server and we were creating railways which had multiple corners and zig zags.  Whenever the mine cart runs into a corner or turn, the cart stops and comes back.  The cart could never pass the railway turns.  Sometimes we were able to force the cart through the rails corners, but the cart would just derail itself.  I have tried it on a single player world and it does the same thing.  Fortunately, the cart has no issues when going in a straight path.  I don't have any type of recording software, so I am not able to get a video of the issue.