Stations stop producing and dont send many goods to eachother

[Orillien]

I have 3 mines and a scrap factory in one system but some of them just stop working. When I reload the game they work for some time but later they stop again. Also if I have my steel and scrap factory and my coal mine in the same system and I set the steel factory to take its goods from the other 2 plants and it does so but in such small amounts that it's completely worthless. All stations are XXL and the steel factory easily needs 100 times as much to be able to work like this. Can someone help me with that ?