Child custody orders are made with the best interests of the child in mind at that time. The issue with these orders is that they can't predict the future. This is where modification orders come into the picture.
Child custody modifications can help to address some of the issues that come up over time. Some situations occur that almost always require that you seek a modification of the current order.
If you or your ex is unable to keep up with the current child custody or visitation schedule, it is time to get it changed. Both parents deserve to be in the child's life, so you may need to work out a new schedule because of a job change or something similar.
If one of you moves out of the area, a new child custody agreement is necessary to address the new living arrangements. This might include a new visitation schedule. It might also include virtual visitation, which can help the parent who moved stay in contact with the child.
If you think your child is in danger, you should seek a modification. This is an accusation that you shouldn't make lightly so make sure that you understand what is going on; however, acting swiftly is sometimes necessary to protect your child in these cases.
You and your ex might be able to work out the terms of the modification together. This is typically a faster and more amicable resolution to getting the problems addressed. Make sure that you carefully consider all necessary points that need to be addressed in the modification.
Source: The Spruce, "5 Reasons to Request Child Custody Modification," Debrina Washington, accessed July 27, 2017