"Mangio una banana."
If you keep encountering problems with the pronunciation it might be a good idea to always use the slowed down version. After a period of time you will know more Italian and will "hear" the right forms. I agree that the voice is not perfect. In real speech you will encounter people speaking indistinctly and your mind will correct automatically. At least that is what is happening in your native language. In a foreign language it is impossible in the beginning but by using the slow version you can train yourself.