I want to clarify before i continue. While i noticed this bug with another mod it DOES occur with vanilla trains and fuel albeit much more rare, which i know because while testing it happened to me using "Train + Nuclear fuel"

So when playing with "Supersonic Trains" anything past "MK1 + nuclear fuel" or "MK2 + coal" the trains move so fast that when they hit the subway they get in this weird (and loud) state where its like trying to move/teleport. In order to fix it you have to pick up the subway than the train, when you pick up the subway it shows the train and at its wheels a white smoke effect(it's also still doing the noise). It also duplicates a few rails.

Trains that are running that fast are almost not handleable, I will think about something that would help. I check trains on specific positions in subways every tick.

Not sure what all is possible, but you could "pre-check" the position of the train. So like based on the speed of the train the further out you check. If the speed is under acceptable speeds it function like normal but if the threshold is surpassed you essentially have the code go "oh hey the train is moving at X speed, i should start the teleport process early so that when it reaches the spot it teleports."

For the MK3 of the supersonic trains, this can be simplified since it moves so fast you could literally teleport it early and most people would not notice.

If not that perhaps the maker of "space exploration" knows the answer because i think their space elevator works fine with supersonic trains.

I think the main issue is that above a certain speed I need to transport more than one carriage per tick...
Could you have a test if it works in SE? I went through the code and it appears to work in the same way

I could but before i do this is a recent youtube video someone made showing it in action. From the look the train slows down before entering. Perhaps thats the issue?
https://youtu.be/hYcAsNCH7Zc?si=eAq2HGTN2DMLdr7C&t=1415

As a workaround, this might be helpful: https://mods.factorio.com/mod/train-speed-limits