Steps:
- Have the mastery for 4 crew members, and have all four active.
- Respec your crew mastery.
- One of your crew members will now be inactive due to not having the appropriate mastery.
- Purchase the 4 crew member mastery again.
- Print the crew member that was dropped.
BUG: The crew member can't gain any levels. You must prestige before that crew member can gain any experience.
(Cyber Specialist specifically is the crew member I saw this with).