This creates a very confusing situation if the player activates both "Like Hot Potatoes" and the "Experimental Field" contract at once, as people often do. Both contracts become available at the same time, both require the same cargo be delivered to the same exact zone which does not indicate which unloading is for which mission, so if the player delivers cargo for "Like Hot Potatoes" - they are then left without cargo for the "Experimental Field". Getting more of that cargo requires them understanding that the "Experimental Field" contract has to be restarted. The issue is compounded by "Like Hot Potatoes" being one and only repeatable contract in the game, which players often activate again without paying it much attention, and end up with two active contracts with seemingly no cargo for either. It's a vicious cycle. 

Solution is simple: "Like Hot Potatoes" should be blocked by the "Experimental Field" contract, so they could not be active at the same time.