Confused about factory maintenance & output

[Morik]

I am playing as the Netherlands and conquered Belgium a while back.
When I'm looking at the factories, I see that my cement factory is producing more cement than it can sell (shows something like: 0.759 of 2.138 didn't get sold).
In another factory in the same state, it shows that its throughput is reduced due to not getting enough maintenance inputs. The only input is cement, and it shows a small shortage.
I am subsidizing both factories.

Why isn't the factory that isn't getting enough cement buying more from the factory that couldn't sell all its cement?
And I've let it run for many days and checked each day--each day there is unsold cement left over, and the other factory isn't getting enough cement...

Screenshots below.

 

[Morik]

Still seeing this... the factory that isn't getting cement has plenty of budget... anyone know what could be causing this, and if it is anything I can fix?

 

[Gnorf]

It's temporarily reducing throughput to avoid overproduction. Most likely the demand on canned food is very low. Stockpile a few hundred and see if there's a difference.

 

[Morik]

Ah, so a factory can deliberately lower its intake of maintenance goods in order to deliberately slow itself down?

Why doesn't it do that when it is producing some goods, and for 3 years straight not selling all of them? (Why not deliberately slow throughput down to the level where no goods are left unsold?)

 

[Hagie Sophia]

I'm wondering this myself. My industry is pretty hobbled right now because many of my factories have penalty due to lack of maintenance goods...except I have plenty of them in national stockpile and/or I have other factories producing plenty of them. What gives??