I could totally have just misunderstood what word I was aiming for or how the mechanics work. If that's the case I apologize!
Sometimes, I wouldn't be able to push a wrong letter off because it is blocked by a correct letter on one side. In this hypothetical, let's say the correct letter was on the left and the incorrect was on the right. If I were to try and push the incorrect to the left, it can't move because the correct letter is on it's left. If I wanted to push the incorrect letter to the right, I cannot because the correct letter is on the incorrect letter's left side, blocking me. Whenever I tried to place a bomb on the correct OR the incorrect letter, I would get a message saying "I can't blow up a correct letter."
I hope this helps!