We have discovered a (I think) new bug. It just started happening recently.
If you have NPC crew that is mounted on something (sails, cannons, etc) they consume food from the food larder, but their food stat doesn't go up. NPC crew that is just standing around sweeping don't have this problem. The issue is that the mounted crew food keeps going down and down and down, even though they are consuming food, and they eventually die of starvation.
You can "reset" it by unseating the crew, then their food stat immediately goes back up to full (if they've been eating).
We've been losing NPC crew left and right and unable to figure out why until I stumbled across this.