i loved this game, it gives such satisfaction to make everything fit!
the only thing i would change is that once a level is finished it would be possible to look at the finished loops, often when i finished a level i was so in it that i hadn't noticed it was going to be done, and then i didn't have time to "admire" it. ;)
i had the same problem and used "report a missing achievement" adding a screenshot and got awarded it, thankyou to whoever does this, that was quick! :)
recommend it to those how had this problem aswell!
 "Submachine: 32 chambers"){kind=icon}
 "Submachine 6: the edge"){kind=icon}
 "Covert Front 3: Night in Zurich"){kind=icon}
 "Little Wheel"){kind=icon}
 "loops of zen"){kind=icon}
 "Perfect Balance"){kind=icon}