The rail line is long and level, with enough powered rails to keep carts at high speed. The "station" has multiple unpowered rails to stop carts.

These work when riding a single cart (stopping it on the first of two consecutive unpowered rails). However, when I have a chest-cart in front of me, both the chest cart and my minecart fly through the "station" without even slowing down.

I can see how maybe the chest-cart could be pushed through two stopping rails, but there's no way that my cart should follow it through without even slowing. Something, perhaps incomplete rendering, is preventing thorough application of rail effects.

Frame rate was 6-8 fps, and I seemed to roll through the station rather than skipping it via freeze-and-jump lag.

Regardless of what may be rendered visually, movement rules should be inviolable. When client and server get all caught up with chunk loading and graphical rendering, I should see myself stopped with a chest cart stopped in front of me.

For the curious, here's the rail pattern in the "station":

Direction of travel --->
==================DP==U=UU=DPP=DPP=========

'=' is plain rail
'D' is Detector
'P' is Powered, but only while detector fires
'U' is Unpowered (stopping rail) at all times

Edit: I've run through the station a few more times. Behavior id fairly consistent, but not completely. If the chest cart runs about 5 blocks ahead of mine, then all power/unpower effects resolve as they're supposed to (chest stops on first U, then I enter and bump it forward and bounce back against the closed one-way DP).

Problems occur if the two carts are in contact (actually overlapping slightly) when they reach the unpowered rail. It's as if my cart is able to bump itself forward – when the unpowered rail is forced to let go of the chest-cart, my cart is so close behind that I get through as well.