I have a Duplicant who was low immunity, 36%, so I assigned her to the med-bed in my medical bay room. When night came, she went to it, and tried to sleep on it, but she couldn't and then she just slid across the tiles (no walking animation and still yawning in a freeze frame) then went to her bed. It looks like this is a small bug with assigning her both a cot and a bed in the med-bay. She also when she is assigned to the med bed only, she goes to it but just sleeps right on the ground next to it, since she's not sick.
Assign a duplicant a med-bed and a cot at the same time