I did the mission a 4th time today (Advanced Combat Training I - Enemy Drones), and it completes but then there is no next mission. So I did all kinds of other missions and my available options are decreasing.
Now I do them over and over again but that kinda gets boring very fast.
I also tried and aborted the mission after accepting, but that didn't change anything.

Now I wouldn't even think it's broken, if someone didn't say the other night that after the Trainings you could be at Combat license level 3 - where I'm still stuck at Level 1.
So I think i'm missing out on some missions here.