Hey Shamasu!
I've pushed a few changes and thanks for flagging them for me to look into on moving trains press + on the line that should receive a train, on a line to send one away. It costs a small depot fee, shown on the button. My own testing shows this is now working but let me know if you get another chance to try it, on the water I saw a failed check happening, I've corrected it now and when testing i'm now seeing it reject it correctly. If you want you can delete the station in the water but otherwise it'll remain there, I'll be pushing changes based on feedback and trying to focus on bugs, feedback and rebalancing for the next few days