As the subject denotes, Dupes continue to randomly suffocate in areas that are completely breathable, while corpses are "suffocating" and other dupes are starving while there is plenty of food available. Their paths are not obstructed, nor is there a warning of starvation or suffocation before death occurs. Dupes who have starved seem to be reading as plants who are not getting the correct conditions for growth. As Good Ol' Chan didn't have any irrigation or fertilizer, he perished of neglect.
Not certain as it seems completely random. Even replaying the save files with no new changes does not cause the issue to re-occur.