If you cannot find the required crew members in the Barracks, they were dismissed when selling vehicles.
You can recover crew members with all their trained perks within 32 days of the moment of dismissal. Read this article to learn how to do it.
If the crew's major qualification level decreases when transferring them to another vehicle (without retraining the crew), it will be displayed on the panel of crew members in the Garage.
If one crew member has a slightly lower percentage of a major qualification (perk) in a particular vehicle than the rest, they have likely been more injured in battle than other crew members.
The game has a limit on hiring free tankers: no more than 20 crew members per 12 hours.
When attempting to dismiss a crew member who has been trained for a vehicle that has been sold and is no longer in the Garage from the Barracks, an error may occur, accompanied by the following message: "Error dismissing a crew member. Wrong vehicle."
To fix the error, restart the game client.
Combat XP is credited to all crew members. However, the required amount of XP increases with each percent of qualification or perk level. Therefore, it may seem that the level of training does not increase.
To see the opposite, click the Quick Training button. More details will be displayed about all crew members' training progress. Fight at least one battle and check the Quick Training menu again. You will see that the information has been changed.