Once they eat one portion of food, they drop the rest on the ground. Cheese spread, milk in a bottle, etc.
Well, just as in real life! I do that all the time 
…
Jokes aside, which version number? Does it happen with food in their inventory or in the basecamp? What mods are activated in your world?
Also, isn’t this the same bug you already posted about?
Sorry, I’m becoming senile it seems!
It must be because it makes playing with NPC needs a big chore. This was from version 2 days ago.
popped cans cannot be contained in inventory so thus they drop em
Spread cheese is dropped also.