It appears that we've encountered a nasty little bug with spawning custom items! The bug is caused by making over custom items prior to their approval by the art team. Essentially, if the custom item is owned by a faction (and potentially dead characters) at the time of approval, the tools can't figure out where to place the item and will crash. This also happens on denial due to the tools not knowing who to refund the CP to.
Because of this, we'd like to ask that people please avoid making over custom items prior to their approval until it is sorted out.