“There are two classes of beings, the fallible and the infallible. In the material world every living entity is fallible, and in the spiritual world every living entity is called infallible. Besides these two, there is the greatest living personality, the Supreme Soul, the imperishable Lord Himself, who has entered the three worlds and is maintaining them. Because I am transcendental, beyond both the fallible and the infallible, and because I am the greatest, I am celebrated both in the world and in the Vedas as that Supreme Person.” (Lord Krishna, Bhagavad-Gita 15.16-18)

Everyone in the material world is fallible, this means everyone can make mistakes and can be wrong. Everyone has limited knowledge, some are experts in one field of knowledge but they will not be expert in all fields of knowledge. The gurus will give knowledge based on their own life experiences, and the knowledge they acquired and understood from what they studied and learned from others.  Gurus can and do make mistakes. 

In the spiritual world, everyone is perfect. Everyone has full knowledge and nobody makes mistakes

Only God has all knowledge and He can never be wrong, nor does He ever make any mistakes.