It appears that when my duplicates were getting hypothermia, there would never go to med-beds whether or not they are in a med-bay. Though it appears that hypothermia only lasts half a cycle. Even when the beds are unassigned and I am getting the no mead-bed warning.
I am not sure, it first happened closer to day 30-40 when I was entering colder climates. It does appear that even when beds are destroyed and rebuilt they still won't use the beds.