Squadron Member didn't receive a new tactic

One time after finishing command mission, one of my squadron members didn't learn anything - no new tactic nor +1 upgrade.
Did it happen to anyone else? Is it a bug or is it intended? Or are there certain restrictions such as squadron level or whichever dungeon you are doing?

I've had that, too. I think they have a good but not 100% chance of learning one.

Seems to be a relatively common occurrence. Quite often only two of my Squad mates will receive a new tactic.

Thanks guys~