Some basic crew operations such as dismissing a crew or sending to the Cryostasis Vault will not work for crew assigned to a Battle Station. In order to interact with them, they need to be released from their post.
In an example below, Immortalized “Dark Ages” McCoy can not be put in the Cryostasis Vault because the crew is assigned to a Battle Station.
You will be prompted with a message that the “Crew is busy!”
In order to release a crew from its post, you will need to start a regular space battle mission.
From the main UI, go to Galaxy Map and travel to Episode 1.
Choose to enter a node that indicates a ship battle.
Select the crew avatar of the crew member you wish to release.
You can choose to leave the post unmanned by tapping the icon or you can replace it with a different crew.
Tap Confirm to save the changes.