Thank you so much. I'm still learning the game. I was wondering what is the purpose of this stack limiting. Now it works fine.

Hi! I'm not sure what is the problem, but what I see on the picture below is:
- blue inserter should load onto the train either coal or empty barrels
- the wagon has filters so there are designated spots for both coal and empty barrels
- there are empty barrels coming along the belt, but the ...