I've tried three different models of bus station, both vanilla, DLC, and modded. I've tried dragging them around with MoveIt, moving them with the in-game tool, and demolishing and re-building them. I've tried different locations. All have the same problem. If I hover over one of the red lines, I get a fly-up message saying, "Path failed, 2/2 (6761 49865)" though sometimes it's 4/4. I don't think I've seen 3/3.
I don't know how to find individual path segments based on their segment number, my googling is not helping. But I don't have any other pathing problems (that I'm aware of, lol), and everything else in my 48k city is working. City busses can make stops within the bus station, adding bus stops within the station to existing routes, or moving existing stops within the station, works fine.
Any ideas what's wrong? Or how I can troubleshoot further? Thanks