Error message yet trains are delivering fine

Hey all,

Just got TF2 yesterday and have been having fun with it. I started a freeplay and now I am getting a strange error message.

I have a loop with 4 stations and several trains running around, but the game says not every station is reachable, WHILE the trains are running fine and delivering/picking up at all stations. Is this an issue with the platforms? Some stations have 2 platforms.

When I look at the line information in the window, it shows a grey line with 1 section being red. Is that where the issue is?

I'll try to upload a screenshot if that would be helpful. Just let me know what information would be most helpful.

TIA