How can you avoid delays during apparel manufacturing?

I'm trying to understand what commonly causes delays when producing clothing. I'm planning ahead because missing a launch date could create problems for a small brand. the apparel partner came up while I was researching different production services. What are the most common reasons apparel orders get delayed? Are material sourcing, sample revisions, production capacity, quality issues, or shipping usually responsible? What can brands do before production begin to reduce the chances of unexpected delays?