My wild guess is seasickness. It's not supposed to happen to astronauts due to training and such, thus perhaps the unwillingness to say who. But tight quarters, seas were rough. You get the other astronauts checked out also just in case. I really don't have evidence for this though beyond wild speculation.
Then why scold SpaceX about safety?
They all get space sick. Training helps with the temporary effects of g but no earthly training can prepare one's inner ear and digestive tract for 24/7 weightlessness. It happens to all of them but, conversely, they all get over it in time.
I've never heard of anyone being hospitalized for motion sickness. Symptoms stop quickly once the patient is back stationary on solid ground.
That’s cause you never had space motion sickness.
There was no decompression.
Decompression sickness requires breathing air at higher than atmospheric pressure, which you only need to do if the external pressure is high (i.e. when diving - otherwise your muscles would be unable to overcome the pressure difference and you wouldn't be able to breathe).