Im not sure if this was a bug or not but at the risk of everyone calling me noob I figured I might as well post it.
Civilian Freight Lines are causing interrupts when they dont have a cargo to load on a planet and a contract set up. For example I set up an infrastructure contract I set up earth to supply say 100,000 and both luna and mars to recive 100,000. I dont actually have 100,000 infrastructure on earth, so when the freight lines use up all the available infrastructure I start getting event messages saying that particular freight line ship cannot load. now when i remove the supply portion from earth, the messages go away, which is why im not sure if they were intended to warn a player when supply ran out, or a just a bug.