Several of the Bombshell achievements on Steam are bugged. One of the ones I was pretty sure I’d completed was “With A Little Help” (Used Amiga to find a secret area). I’ve used the teleporter on Kyrron dozens of times, and it never gave me the achievement.
I’ve always played with an Xbox 360 controller, so recently I figured I’d try doing with the keyboard and mouse. Sure enough, I got the achievement.
So, for anyone out there who’s having trouble with bugged achievements, apparently your controller can make a difference.
EDIT: I had hoped some of the other bugged ones would pop if I kept playing with the mouse and keyboard, but so far no luck. It may have been unrelated, then.