If I understood the scenario correctly, you can't push the duo of blocks upwards because one of them (the one with an extra inner outline) doesn't accept multipushing. You can see the same in level 3 if you try to push the two blocks in the center of the level to the right together vs. pushing them to the left. (You can press control + Q in almost all of the covemountlikes to skip levels if you want to quickly get back to where you were)