I wrote this one in 2018
Titan behavior is different than human behavior in several ways.
Titans are protective of their bonded person. Titans will usually follow the orders of a person they bond with for a unending amount of time (see the nature of tomb, treasure and property guarding Titans) unless they bond to a new person.
There are some situations in which a titan might disobey their bonded. Most of the time this is because the titan is too strong for the person or the person is not like the former bonded. For a titan than is fully bonded and useable by the bonded, disobeying usually occurs to save or guard the bonded's life. There are also cases of titans bonding only to people who possess certain criteria. These titans often (those more likely to happen if newly bonded) will not follow their bonded or even let them summon them if the bonded does not display these characteristics.
Titans are also slow to fully comprehend a situation. This can cause problems in some cases because they might misinterpret the situation and try to protect their bonded in a way that actually make things worse.