I noticed that the recruits in my pool are still stuck at a low level. I've read that they are supposed to gain experience after every mission, even when not deployed, and yet some of my recruits are still at level 3. My MC is level 12 and I already dealt with the super mutants.

Did I break the game somehow? I'm using version 1.27, with the only mod being the one that fixes burst fire instant killing your troops when it misses.