Although tracking AF on Galaxy S6 is on, tracking a subject may fail. What should I do?

Please note tracking a subject may fail in the following conditions:

• The subject is too big or too small.
• The subject moves excessively.
• The subject is backlit or you are shooting in a dark place.
• Colors or patterns on the subject and the background are the same.
• The subject includes horizontal patterns, such as blinds.
• The camera shakes excessively.