Out of nowhere, trains are suddenly having their deliveries changed mid trip. So they load half the cargo they are supposed to load (say copper) and while they are loading, the train gets a whole new trip assigned (load plastic) and ends up delivering the copper and plastic to the plastic unload, polluting the system.

Good day.
Tell me, was there anything that preceded this behavior? Maybe you attached or detached cars or something similar was done by another mod?

Could you post a save with this problem?