Is it possible to get a the timetable sim to only simulate one month for layers? The issue I'm facing is I've got a layer for May with a train that does a run across the map and back. I've then got another layer for July where a different train does a run across the map with the same timings as the May layer. When I run the simulation the whole timetable locks up because it's trying to run both trains at the same time.
You cannot have trains from different seasonal layers conflict with one another in this way. Even if a seasonal layer only shows up in the "background" in the period specified, players can still choose to play the May train in July, so the timetable still has to work with all seasonal layers active at the same time.