Resources are shown as needed but are full

Hey guys,

I have a real problem. While I am playing more towns in one region, the small icon of the other town shows a red symbol that a resource is needed (see attached picture).

But my mines are working and full just like my transshipment warehouse.

Is that a bug? For short time it helps to buy new transshipment warehouses but the warning comes back after a short time.

This problem is in other regions too.. 

Ty for you help