I think I know the situation.

When we pronounce a sound in different words, sometimes the sounds before and/or after it have an impact on it. If you can say 'spoon' correctly but not 'moon', 'rake' but not 'ray', one of the most likely reason behind is that you haven't grasped these two vowels.

As starnight mentioned earlier, you don't have to say every sound perfectly. It takes time.

You are welcome to take further discussion with me to QQH.