Players should not enable a role that they are unwilling to play. Station staff players generally cannot abandon their roles, but there may be exceptions when it is the result of good roleplay. If it is the result of good roleplay, and the roleplay reason for leaving the position is outside of the control of the player leaving the position, it is extremely unlikely that it would be an issue. Players can do things unrelated to their role or their role’s job when nothing important needs to be done related to their role. What is considered important varies, but for command it generally includes any department management. For all roles, receiving an order from a superior typically means you should be doing something related to that role, even if you are not following the order. Except for security and command, changing jobs is not considered abandoning a role.
Passengers are not staff and do not have a job or role to abandon unless they change positions during the round.