Yeah I couldn't really think of how the pathing algorithm would account for this, unless the roundabout was split into different regions. Any suggestions on how to change the signaling to prevent this? I'm not sure if there's enough space to increase the roundabout size. Or I could resign myself to ...

I've occasionally noticed situations where my 2 locomotive + 8 cargo wagons trains are crashing, and I eventually isolated it to cases where they crash with themselves . I've attached a save file from ~5 seconds before this happens, and can include additional saves up to about 3 minutes in advance ...