If your industry is segregated, how does your "unique factory products" get to commerce, so they don't import it?
Do you have any yellow zoned "generic industry" zoned?
What is your unemployment rate in your population menu? Unemployment drives demands. It must be 5% or higher at all times.
You should be ignoring commercial demand at all times. It is optional and you can create office jobs instead to keep freight demands down and also fill employment demands. Commerce should be very small and only where you want it. I mean commerce can be as big as you want. But don't follow the commerce demand at all.