iirc, every time they level up, officers are supposed to be able to choose between gaining 3 ranks in one of the skills they already know and gaining a new skill at rank 1. but one of my officers who just leveled from 4 to 5 (and has a total of three different skills so far) only gets to choose between ranking up two skills she already knows.
full screenshots:
i assume this is a bug, likely caused by the fact that she had enough accumulated xp to gain three levels in a row: i just gave her the rank 1 Gunnery Implants as she leveled from 3 to 4, then immediately got to level her up again.
in case it makes any difference: she had the other skills from the start, as i hired her at level 3. so this was the first time i leveled her up myself.
level 5 to 6 seemed to work as intended.